I prefer flawed magic items to be the results of mistakes or errors or attempts to make magic items that do impossible things (even for magic), rather than malicious curses.
Amulet of Heath -- This amulet appears to be made of toffee covered in milk chocolate. Because it is. The amulet is edible and contains four uses. The amulet otherwise behaves as though it were a Restorative Ointment, except it must be eaten to be used.
Dwarf Thrower [A] -- Required attunement by a Dwarf. This magical warhammer gains +1 to Attack and Damage rolls. Dwarves attuned to the weapon have the Thrown weapon property, with a normal range of 20 and a long range of 60 feet. The warhammer uses the attuned dwarf's attack rolls, and a dwarf thrown by this weapon deals damage equal to that dealt by the dwarf thrower when weilded by the dwarf. Immediately after the attack, the dwarf files back to where the weapon awaits, with the dwarf always landing on his or her feet and again wielding the warhammer. A thrown dwarf in heavy armor suffers no ill effects from being thrown, although may suffer effects from contact with the enemy such as contact damage with a fire elemental if the attack hits the target. A thrown dwarf not in heavy armor suffers 1d4 bludgeoning damage if the attack hits the target.
Invisible Ring -- While attuned to this ring and when the command word is spoken, this ring turns invisble. It remains invisible until removed. The wearer is unaffected.
Ring of Spell Turnning [A] -- While attuned to this ring, whenever you are the target of a spell cast by a hostile creature this ring activates automatically. The ring vibrates slightly, and the voice of a young girl may be heard: "Turning. T-U-R-N-N-I-N-G. Turning." Sometimes appears as "Ring of Spelling Turning," "Ring of Spell Storring," or "Ring of Spelling Storing."
Robe of Useless Items [A] -- This robe has cloth patches of indistinguishable shapes and colors covering it. While wearing the robe, you can use an action to detach one of the patches, causing it to become the object or creature it represents. Once the last patch is removed, the robe becomes an ordinary garment. Each robe has two of the following patches:
- Dull butter knife
- Used torch
- A small pumice stone
- A torn sack
- 50' of hempen rope in a single large Gordian knot
- A 10' palm frond
Additionally, the robe contains 4d4 other items of similar value:
- A sack full of goose feathers
- A bag of obviously counterfeit coins (wrong shape, wrong denomination, clearly not precious metals)
- A life size painting of an iron door
- A wooden ladder (2.4 feet long)
- 4 empty potion vials
- A rowboat (6 ft, no oarlocks)
- A 5' square table with only a single corner leg
- A dead riding horse, complete with saddle with broken or missing straps
- Etc.
There is a 1% non-cumulative chance each week that one of the patches will spontaneously become a patch for a Robe of Useless Items. No robe may ever have more than one such patch, though robes created by such a patch may.
When all patches are used, the robe instantly crumbles to ash and dust.
Rod of Adsorption [A] -- When gripped firmly and activated, this rod melds and sticks to anything it touches, including the wielder, for one hour. A DC 20 Strength (Athletics) check can break contact with the rod, but whenever an attempt is successful there is a 50% chance that some other creature or object adhered to the rod instead breaks free. Any creature becoming unstuck from the rod before the effect ends takes 1d6 damage. The rod may be used once each day and recharges at dawn.
Rod of the Ruler [A] -- You can use an action to present the rod and know the exact distance between any two points you can see. You can also determine if any two points are level or plumb, and whenever you draw a line you may choose for it to be a perfectly straight line or perfect curve of the desired type.
Staff of the Magoo [A] -- This staff functions as a
Staff of the Magi, except any caster attuned to it becomes affected by a permanent
confusion spell. By mysterious consequences, no matter what actions the attuned caster takes, no damage is ever dealt to any creature as a result of them, though significant damage may be done to objects or the environment.
