I recently gave this one to my Epic (Average party level 28) PCs. Be warned, as written it's hideously powerful, but could be toned down fairly easily and still keep much the same flavour:
First Blood (Major Artifact)
Appearance
First Blood is unusual for a weapon of its power in that it appears entirely mundane-more than a little shabby, in fact, its leather bound hilt tattered around the edges and stained in a few places, its blade bearing the first signs of rust, and an empty, slightly pitted setting in its hilt which may once have held a gem or holy symbol.
Game Mechanics
First Blood is most usually a +8 Wounding Longsword of Speed. However, as a free action, its wielder may change First Blood to any simple or martial weapon of his or her choosing. If used as a ranged weapon, First Blood bears an enchantment which automatically creates ammunition whenever it is fired. First Blood may be granted the additional capability to change into one exotic weapon of the wielder’s choosing by means of a Wish spell.
The wielder of First Blood always goes first in any combat situation; as long as the weapon is held, his or her initiative is always counted as one higher than the next highest result of the other participants in the combat. If the wielder does not wound at least one foe during his first turn in combat, however, this benefit is lost until the following day.
During the first round of combat only, the wielder may make a full attack action following a move or charge.
The wounding power of First Blood is more potent than normal, causing 1d6 points of damage on subsequent rounds for each successful hit until the target receives magical healing.
On a successful critical hit, the wielder of First Blood immediately gains an extra attack on the same target, made at the same attack bonus as the critical hit. Starting the following round, the wielder is automatically hasted for ten rounds.
And one I made a while ago, which was the primary weapon of our arcane archer for some time- they got this around 15th level, I seem to remember:
Rithrysear, the Storm of Chaos (Major Artifact)
History
The identity, or even the nature of it’s creator is unknown, but most sages agree that Rithrysear was forged in the depths of the plane of pure chaos, Limbo, and for several hundred years served a long line of archers, from noble Myth Drannan knights to the vilest demonic princes- there was only one documented thing any of these warriors had in common- that they were never quite able to fully control the chaotic energy that gave the bow its power. The last sighting of Rithrysear in Faerun was when it was wielded by a tiny Halfling scout, Pedpenel Stoutheart, in the defence of his tiny village in the Dalelands, over 800 years ago. How the weapon even came to be on the prime material plane in the first place, is unknown, although it is most likely a planar traveller came across it whilst traversing Limbo.
Appearance
Rithrysear appears to be hollow, made of glass or fine crystal, inside which a cloud of multicoloured gas boils and seethes. The gas inside the bow provides illumination, made up of continuously shifting colours and degrees of brightness, if the wielder is in darkness. The identifying runes on the bow identify it in the tongue of whoever is reading at the time. Despite its fragile appearance, Rithrysear cannot be broken or destroyed by any normal means.
Game Mechanics
1 Rithrysear is a +2 chaotic longbow
2 Whenever Rithrysear is drawn back, a randomly determined arrow is produced- roll 1d20 and consult the table below to determine type. The wielder understands, in the split second before loosing the arrow which type has been created, and each different type of arrow has a corresponding coloured fletching. Each arrow does 1d8 damage + any bonuses the wielder may have + listed effect on a successful hit. The random effects are not multiplied on a critical hit.
3 A limited wish, wish or miracle spell enables the wielder of Rithrysear to choose which type of arrow the bow creates when drawn back, for one round per character level.
4 A lawful creature that wields Rithrysear gains two negative levels, which cannot be removed or dispelled by any means while he or she possesses the bow.
5 The magic in Rithrysear creates an arrow whenever it is drawn back.
6 The DC for any of the effects, where applicable, is 22. A wish or miracle spell cast on the bow by a chaotic-aligned character can increase this DC by 2 points per casting
Rithrysear, the Storm of Chaos: Weight: 3lb Caster Level: Varies Prerequisites: n/a (artifact)
1
Ysgard: Purple- Arrow casts a cure critical wounds spell on the target, healing 4d8+15 points of damage
2
Limbo: Swirling Black- Target must succeed at a will save, or be affected as by a confusion spell, for 5 rounds
3
Pandemonium: Crimson- Target must succeed at fortitude save, or be blown back 10 ft (which may leave it open to attacks of opportunity.). If the creature is flying by any means, this increases to 15ft. If there is no room for the target to move back, he instead falls prone.
4
The Abyss: Swirling red- Arrow does 2d6 points of acid damage on a successful hit
5
Carceri: Grey-green- Target must succeed at a fortitude save or be held, as by a hold monster spell, for 5 rounds.
6
Hades: Dark red- Arrow gains the unholy property, doing an additional 2d6 damage to good aligned targets.
7
Gehenna: Bright red- Target is affected by an inflict critical wounds spell (4d8 +15 points of damage, will save for half)
8
Baator: Red and black- Arrow gains the seeking property, negating any miss chances that would otherwise apply to the target
9
Acheron: Metallic red- Arrow gains the wounding property, doing an additional 1 point of damage each round, until the target receives magical healing
10
Mechanus: White- Target is affected by a targeted dispel magic, caster level 10.
11
Arcadia: Pale yellow- Arrow gains the merciful property, dealing an additional 1d6 points of subdual damage to the target.
12
Celestia: Brilliant yellow- Arrow gains the holy property, going an additional 2d6 damage to evil creatures.
13
Bytopia: Dark yellow- The area around the target is lit as if by a daylight spell for 10 rounds.
14
Elysium: Dark green- Bow gains the brilliant energy property, ignoring any armour bonuses to AC
15
The Beastlands: Emerald green- Arrow gains the speed property; after shooting with this arrow, roll again immediately; you may shoot an additional arrow with this attack
16
Arborea: Bright blue- Arrow gains the keen property, and threatens a critical hit on an attack roll of 17+
17
Elemental Plane of Fire: Flickering green- Arrow gains the flaming property (+1d6 fire damage), or flaming burst (+2d10 fire damage) on a critical hit
18
Elemental Plane of Air: Flickering white- Arrow gains the shock property (1d6 electrical damage), or shocking burst (2d10 electrical damage) on a critical hit
19
Elemental Plane of Water: Flickering blue- Arrow gains the frost property (1d6 cold damage) or icy burst (2d10 cold damage) on a critical hit
20
Elemental Plane of Earth: Flickering grey- Arrow gains the thundering property, doing 1d6 points of sonic damage, on a critical hit the target is instead stunned for one round.
I have a few more if anyone needs really powerful weapons for their PCs!
Ellie.