I cleaned up this info a bit and brought it all together from what was originally 4 posts... these are excerpts from 1993's 2E monstrous manual. just to get some research done, and provide a few more examples. i’m going to expand the criteria of my search to include alchemical uses of creatures as well as using parts for other protective measures (but not purely monetary value of parts), since not all of them yield magical results.
Aboleth slime is sometimes used as a component for potions of water breathing.
Dried and cured ankheg shells can be made into armor with an AC of 2, and its digestive enzymes can be used as regular acid.
If an aurumvorax is killed with a minimum of cutting damage to its hide, the hide may be turned into a garment of incredible strength and beauty worth 15,000-20,000 gold pieces. The garment will also protect its wearer as armor, the specific Armor Class depending on the size of the aurumvorax. A garment with AC 2 weighs 50 pounds, one with AC 3 weighs 40 pounds, and one with AC 4 weighs 30 pounds.
The wearer also receives a +4 bonus on saving throws vs. normal fires and a +2 bonus on saving throws vs. magical fire.
If an aurumvorax is burned in a forge, approximately 150-200 pounds of gold are left behind. This burning process is very difficult and usually takes between one and two weeks to perform. Of course, the hide may be removed before the creature is burned; if burned at the same time, the hide will provide an additional 21-40 (1d20+20) pounds of gold.
The bombardier action of this beetle is caused by the explosive mixture of two substances that are produced internally and combined in a third organ. If a bombardier is killed before it has the opportunity to fire off both blasts, it is possible to cut the creature open and retrieve the chemicals. These chemicals can then be combined to produce a small explosive, or fire a projectile, with the proper equipment.
The chemicals are also of value to alchemists, who can use them in various preparations. They are worth 50 gp per dose.
Fire beetles have two special glands above their eyes and one near the back of their abdomens. These glands produce a luminous red glow, and for this reason they are highly prized by miners and adventurers. This luminosity persists for ld6 days after the glands are removed from the beetle, and the light shed will illuminate a radius of 10 feet.
The light from these glands is "cold" -- it produces no heat. Many mages and alchemists are eager to discover the secret of this cold light, which could be not only safe, but economical, with no parts to heat up and burn out. In theory, they say, such a light source could last forever.
Behir are useful to mages, priests, and alchemists for a number of concoctions. The horns of a behir can be used to brew the ink necessary to inscribe a lightning bolt scroll, and the sharp talons can likewise be used by a cleric to make the ink for a neutralize poison scroll. The heart of the behir is one of the more common ingredients for ink for a protection from poison scroll.
The scales are valued for their hardness and color, and are worth up to 500 gp to an armorer who can use them to fashion a highly ornate set of scale mail armor.
The smaller eyes of the beholder may be used to produce a potion of levitation, and as such can be sold for 50 gp each.
The death kiss has an organ in the central, upper body that is a valued ingredient in magical potions and spell inks concerned with levitation (and may be sold like beholder eyes). In addition, a brain or nerve node, deep in a bleeder's body hardens into a soft-sided, faceted red gem upon the creature's death. Called "bloodeyes," these typically fetch a market price of 70 gp each. They are valued for adornments since they glow more brightly as the wearer's emotions intensify.
There is only one known benefit to the existence of the bulette: The large plates behind its head make superb shields, and dwarven smiths can fashion them into shields of +1 to +3 in value. Some also claim that the soil through which a bulette has passed becomes imbued with magical, rock-dissolving properties. Many would argue, however, that these benefits are scarcely worth the price.
The filaments of the cave fisher are highly prized by many thieves' guilds, for they can be made into thin and very strong rope which is nearly invisible. The filaments are wound onto reels and then specially treated to dilute the adhesive. The resulting strands are made into ropes, while the diluted adhesive is turned into a special solution, which when applied to gloves and boots, greatly increases traction for climbing.
The feathers of the cockatrice are prized by certain wizards as many magical scrolls must be inscribed with pens made from such quills.
It is rumored that the powdered marrow from a crypt thing's bones can be used to create a potion of undead control. In addition, anyone who employs the bones of a crypt thing to manufacture a set of pipes of haunting is 80% likely to create a magical item that imposes a -2 penalty to its victims' saving throws and has double normal effectiveness if the saving throws fail.
Displacer beasts have little to fear from other large predators, save perhaps trolls or giants. Some wizards and alchemists value their hides for use in certain magical preparations, and will offer generous rewards for them. The eyes of a displacer beast are a highly prized, if uncommon, good luck charms among thieves who believe that they will protect the bearer from detection.
The body of a destroyed dracolich crumbles into a foul-smelling powder within a few hours; this powder can be used by knowledgeable wizards as a component for creating potions of undead control and similar magical substances.
Dragon Hide: Dragon skin is prized by armorers with the skill to turn it into shields and armor, valuable because of its appearance and the protection it affords. Dragon armor grants its wearer an Armor Class of 4 less than the Armor Class of the dragon it was taken from, for a minimum Armor Class of 8. For example, armor from a juvenile brass dragon (AC O) grants its wearer AC 4. Dragon armor is supple and non-bulky, weighing only 25 pounds.
The scales of gem dragons take on properties of actual gems; they are faceted and reflect light. They are slightly more brittle than those of other dragons, so armor made from them requires repair more often.
Dragon armor affords no extra protection, such as resistance to fire or cold, although the armor can be enchanted to provide such protection. A dragon's resistance to certain elements is based on its total makeup, not just its skin. Plain dragon armor is expensive to make, costing 1,000-10,000 gp, based on the workmanship and protection the armor affords. Dragon skin armor can be enchanted, just as other forms of armor can, to a maximum of +5.
Dragon shields also offer no additional protection. They are made of stretched hide over a wooden frame. Such shields weigh 3 pounds (if small) or 8 pounds (if large) and cost 20-120 or 30-180 gold pieces.
Dragon turtle shells make outstanding shields and armor. Because of the shell's strength and natural resistance to the dragon turtle's own breath weapon, armor or a shield made out of this material gains +1 to its defensive rating. The shield or armor will also save as an item against destruction by fire or steam-based attacks at +4.
Firedrake blood can be kept, in its liquid state, in a sealed and airtight container, or under water or some other inert liquid. It can then be used as a firebomb, equivalent to a torched flask of oil, or used to create flaming weapons. For instance, swords dipped in the blood immediately become flaming swords for 3-6 melee rounds, although the sudden, intense heat upon the blade creates a 2% cumulative chance per round of the sword breaking upon impact with each blow struck during the period in which flame engulfs it. After the flame ends, the sword is otherwise unaffected.
Sandlings have little effect on an ecosystem, taking only a fraction of the minerals in any parcel of land. Dwarves sometimes seek them in hopes of finding a rich mineral deposit. They are said to be excellent ingredients for mortar, but they and many druids object to this treatment.
(Salamanders) These fiery creatures' ichor is useful in the creation of potions of fire resistance, and the metal of their spears can be used to create rings of fire resistance.
Nereid shawls command handsome sums, but are seldom sold and are very rare. One who holds a shawl can use the enslaved nereid as a guide on the plane of Water.
When a tempest is killed, a silver residue rains down from its form. If carefully gathered, this residue provides a mass of silver equivalent to 3d6 silver pieces. Though valuable as a precious metal, the silver can also be used as a component in making a wand of lightning or casting a weather-related spell. Bits of the silver are also useful for making other weather or elemental related magical items.
Ecology: The drow produce unusual weapons and clothing with quasi-magical properties. Some scribes and researchers suggest that it is the strange radiation around drow cities that make drow crafts special. Others theorize that fine workmanship gives their wonderfully strong metals and superior cloth its unique attributes. Whatever the reason, it's clear that the drow have discovered some way to make their clothing and weapons without the use of magic.
Direct sunlight utterly destroys drow cloth, boots, weapons, and armor. When any item produced by them is exposed to the light of the sun, irreversible decay begins. Within 2d6 days, the items lose their magical properties and rot, becoming totally worthless. Drow artifacts, protected from sunlight, retain their special properties for ld20+30 days before becoming normal items. If a drow item is protected from direct sunlight and exposed to the radiations of the drow underworld for one week out of every four, it will retain its properties indefinitely.
Drow sleep poison, used on their darts and javelins, is highly prized by traders on the surface. However, this poison loses its potency instantly when exposed to sunlight, and remains effective for only 60 days after it is exposed to air. Drow poison remains potent for a year if kept in an unopened packet.
Ettercap poison is highly valued, partly because of its extreme toxicity and partly because it is rather difficult to obtain. An ettercap's poison glands hold only one ounce of poison at any time, but this ounce is worth up to 1,000 gp on the open market.
Shrieker spores are an important ingredient in potions of plant control.
Reptilian gargantua have two properties useful to humans:
The petal of any flower that grows in the footprint of a reptilian gargantua can serve as a component for a potion of growth. Such a flower must grow naturally in the footprint; it cannot have been planted there by a human or other intelligent being.
As noted above, thunderstorms occur when a reptilian gargantua is born. If a dead creature of any kind is struck by a lightning bolt from such a storm, the bolt acts as resurrection spell.
The silk of insectoid gargantua larvae can be woven into cloth from which magical robes are created.
The horn of the gargoyle is the more common active ingredient for a potion of invulnerability and can also be used in a potion of flying.
Gorgon blood, properly prepared, can seal an area against ethereal or astral intrusion; their powdered scales are an ingredient in the ink used to create a protection from petrification scroll.
In addition, the hide of a gorgon can be fashioned, with considerable work and some magical enhancement, into a fine set of scale mail. This armor will provide the wearer with a +2 bonus to all saving throws vs. petrification or flesh-to-stone spells.
A grell's paralytic poison cannot be extracted from the creature's body, but parts of the monster's body can be used for spells or items relating to levitation or electricity.
Powdered heucuva bones may be used in the preparation of magical items intended to corrupt the spirits of living beings or to control undead.
The hook horror's exoskeleton dries and becomes too brittle for use after a month or so.
Mind flayers raise intellect devourers, treating the ustilagor as culinary delights, and using adults as watch dogs. Both forms of the creature can be used as components in items and potions related to ESP and mind control.
Still, some mages prize the leucrotta hide for creating boots of striding and springing, hoping that the surefootedness of the beast passes down to the boots themselves. There are rumors that leucrotta saliva is an effective antidote to love philters, but so far there have been no volunteers to test this theory.
Lizard man eggs are bitter and inedible, as is their flesh, but their skin is sometimes worked as scale armor (Armor Class 6).
The lurker flies by means of gases generated into sacs. These gases may be used in the preparation of a potion of levitation.
Along with glue, [mimics] can excrete a liquid that smells like rotting meat; this attracts smaller, more common prey (usually rats). Mimic ichor is useful in the creation of polymorph self potions, and their glue and solvent sacs can be sold to alchemists. Other internal organs are useful in the manufacture of perfumes.
Mind flayer ichor is an effective ingredient in a potion of ESP.
Minotaur components are sometimes used in spells and potions, and might be used in magical items involving strength, location, and misdirection.
Though no uses have been recorded for a mudman's mud, it is logical that mages would not ignore its magical properties.
Mummy dust is a component for rotting and disease magical items.
Alchemists have found a number of uses for myconid spores, typically in poisons and potions of delusion.
[Naga] hides can be fashioned into scale mail +2, and their eyes and teeth have been sold for use in arcane spells.
Dark nagas are quick to plunder fallen foe, swallowing items, scrolls, and spellbooks to spit forth later -- for all dark nagas have a bag-like internal organ that they can use to carry things. This organ has thick, rubbery air-sac walls to protect the naga against sharp points and the like, but it also protects the cargo against digestive juices, and has the unusual side-effect of shielding magic from all detection spells.
If a man is kissed by a nymph, all painful and troubling memories are forgotten for the rest of the day -- this may be a boon to some and a curse to others. A lock of nymph's hair can be used to create a powerful sleeping potion or, if enchanted and woven into a cloth and sewn into a garment, will magically add one point to the wearer's Charisma. The tears of a nymph can be used as an ingredient in a philter of love. If a woman bathes in a nymph's pool, her Charisma is increased by two points until she bathes again.
Giant octopi's leathery hide is tough and waterproof, and it is worked into fine rain ponchos by sailors lucky enough to catch and kill one. Another byproduct of these monsters is their ink -- they are most often hunted for this commodity. Giant octopus ink can be used to pen magical scrolls.
Of all magical or enchanted creatures, the phoenix is perhaps most sought after by alchemists and sages alike. There is almost no part of a phoenix that cannot be used in a magical potion or for research.
The feathers of the phoenix have a great many uses. They can be used to adorn a staff of healing, they can be used to make potions of extra-healing, and have many other healing, magic uses. The eyes, beak, and talons of a phoenix are very valuable in the open market, often commanding 5,000 gp and up.
Because of its powerful attractive ability, the nectar of mantrap flowers is an ingredient in a philter of love.
A potion of forgetfulness can be distilled from obliviax, and its spores can be used to make an elixir to restore the memories of the forgetful or senile.
Rakshasa essence can be an ingredient in a potion of delusion.
The heat secretion of a rhemorhaz, thrym, is valuable as a component for heat-related magical items and can be sold to alchemists for 5-10 gold pieces per flask. The remorhaz will contain 10 flasks worth of thrym per Hit Die.
It is said that roc feathers can be used in the manufacture of Quaal's feather tokens, as well as wings and brooms of flying.
The glue from a roper's strands is prized by alchemists, as are its digestive acids, which must be stored in platinum vials.
Korred pouches contain hair, shears, and other items. These items turn to gold (5d4x10 gp value) if sprinkled with holy water. A korred will not voluntarily give up this pouch.
Alchemists and assassins prize the scorpion's venom because of its potency.
The skin of a giant constrictor snake is too thick and stiff to be workable, and is valuable only as armor, not for decoration. An uncured hide can fetch 20 gp.
Few useful by-products can be obtained from a winged serpent. Their poison decomposes almost immediately after exposure to air, and their hide is too thin and fragile to serve as good leather. Their wings, however, if powdered and mixed with ink, can be used to inscribe a protection from lightning scroll.
Sprite sleep ointment is concocted from forest mushrooms. The ointment must be left to cure in the sun for seven days. Sprites hollow out tree stumps to serve as containers for this rare substance.
The most famous by-product of pixies is pixie dust, also known as dust of disappearance. Crushing 50 pixie wings into a fine powder creates one dose of dust of disappearance. Naturally, pixies frown on this use of their wings.
Legend says that a great treasure can be extracted from the tarrasque's carapace. The upper portion, treated with acid and then heated in a furnace, is thought to yield gems (10d10 diamonds of 1,000 gp base value each). The underbelly material, mixed with the creature's blood and adamantite, is said to produce a metal that can be forged by master dwarven blacksmiths into 1d4 shields of +5 enchantment. It takes two years to manufacture each shield, and the dwarves aren't likely to do it for free.
{Giant toads’} skin can be fashioned into suitable leather armor, but its odor will be at least as distinctive as its appearance.
The troll's green blood is used to manufacture both poison antidotes and healing potions. The blood from one troll, worth 400 gp, can make three such potions.
Ice troll blood is frequently used in the manufacture of frost brand swords, and rings of cold resistance.
The secret to this longevity is the strong magical nature of the horn. Unicorn horns are highly sought after, since possession of one is a sovereign remedy against all poisons. Alternately, a single horn can be used, by an alchemist, to manufacture 2-12 potions of healing. Unicorn horns sell for 1,500 gold pieces or more on the open market.
Inside each urchin is a crystalline organ-gem that seems to have some connection to their innate clairvoyance ability. While this gem has little value as a stone, it is highly prized by alchemists. The exact value of the organ-gem depends on quality and the type of urchin it was taken from. To determine a stone's value, consult the "Treasure" entry above.
(Black - 10 x 1d10 gp, Green - 40 x 1d10 gp, Red - 90 x 1d10 gp, Silver - 250 x 1d10 gp, Yellow - 160 x 1d10 gp. Land urchins have no organ-gem but often (80% chance) form pearls inside their bodies. Old urchins contain 2d6 such pearls, each valued at 1d6 x 100 gold pieces.)
Certain body parts {of a wyvern} are used by spell casters as spell components, for which they will pay a reasonable price. {note that the specific parts are not mentioned here}
Yeti fur ... is prized by those living in cold climates for its extraordinary ability to keep its wearer warm. A full grown yeti pelt can fetch up to 300 gold pieces on the open market.
