RPGMemes

Ring of protection. Grants everyone around you protection in a fairly large radius. Might be useful for long range combat, maybe. Might also be useful to navigating certain environmental hazards.

Boots of Flying. They can fly, but only have a carry weight of a few pounds. If you're more than say ten pounds, the little wings flap but gain no altitude. They are not autonomous. Might be useful in condunction with other magics to reduce weight.

Gauntlets of Ogre Might. Do not affect strength. They do tell you the odds of nearby ogres taking particular actions. They might do this, they might do that, and so on.

Hammer of Striking. Social bonuses when organizing labor. Combat bonuses only when near many allies.

Boots of Haste. Gain extra actions but large penalties to all checks. Haste makes waste. May be useful if combined with large bonuses or fixed outcomes (eg: DND diviner wizard).

Circlet of human perfection, but the creator had a really niche fetish.

Lembas bread but it's 1000 years past it's due date and you will get diarrhoea equivalent to its food value.

Helm of Invincibility: you are invincible, but only to people who have Vince in their name, e.g. Vince, Vincent, some other name with Vince

Invisibility potion that turns your digestive track and stomach contents invisible.

Flail of Flatulence: deals an additional 1d4 of embarrassment to the target while dealing 1d4 of gas damage to everything within 6 meters.

Periapt of health: this is a small vial with a red liquid inside attached to a small chain. While wearing this, all diseases that you would otherwise contract enter the small vial instead. If the vial is broken, the closest creature will immediately contract all diseases contained within.

Deck of many things (used): the previous owners of this deck got all that they could have wished for. The remaining cards might not be the best.

Ring of mind shielding: the creator of this ring was a bit over-zealous. Along with the usual effects, this ring will censor violence, sex, and other uncouth things.

Cloak of the bat: along with the usual effects, wearing this cloak will also make you speak bat. You will only be able to produce high-pitched squeaks.

Portable hole: this portable hole is bottomless! Anything that falls down the hole is lost forever.

And I'm stealing that idea for my game, and that one, and this one is cool too ...

Arrows of Accuracy: These arrows will always hit. Starting from the target, then out from that point, the hit roll is checked against defenses.

If nobody is hit, the arrow strikes the firer.

The "Sword of Instant Regret". It does 100% DMG, but only stabs the wielder.

Magic sword of infinite sharpness.

Sheathing the sword, or holding it by the hilt, quillons, or pommel causes it to become incredibly heavy.

Bead of (Uncomfortable) Nourishment: Standard effect, but must be taken nasally. Oral absorption may cause permanent magical flatus.

Sword with fire enchantment, fire has no regulator and cannot be turned off.

Leaky alchemy jug.
Whenever you use this jug roll a d100. This is how many percent of your choosen liquid are replaced by mayonnaise.

Skull of Corruption: It can do damage, but most of the time to your invaluable backup files.

Not quite the same, but a Paladin in a campaign I was in once bought a Shield of Missile Attraction for cheap because the shopkeep thought it was cursed.

Wand of Wonder What This Does

A regular wand of wonder that comes with a gambling addiction.

Bag of holding with a preexisting hoarding problem

Can’t-trip - only works when you don’t want it to

Book of spells, but you have to spell out letter by letter each time you cast

I have a spreadsheet full of these somewhere. The 2 that my players got that I remember them using are:

Emperors armor: +3 full plate armor with no strength or armor proficiency requirement. When you look at yourself or in a mirror you see yourself in full plate armor, but to everyone else you are naked and if anyone tells you that you are naked the armor and all your possessions cease to exist. My player made it the shopping district in the heart of the city before someone told him.

Staff of disintegrating: when activated, it disintegrates. The player that got this one saved it for a boss fight. He found it hilarious though.

Immovable Rod: Only one end of the rod is fixed in space, the other end swings freely.

Sword of Bludgeoning

+5 impact damage -2 stab damage

Only 10% off, because pommel strikes are op