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.

“Wizards with Guns” did a couple of sketches based on this concept.

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).

Never starve again with their endless supply of pies!

Probably bad that without the parentheses, I was already assuming this was some kind of horrific Sweeny Todd situation.

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.

Ring of invisibility. Makes you invisible, but makes everyone else invisible to you as well.

Or makes you smell horrible. Yes I just stole this from ‘cruelty squad’.

The periapt of health also keeps you from the fun effects of drugs (including alcohol); not useless, but keeps working for 24 hours after you take it off

Deck of many uncomfortable things Normal mix of good and bad, weak and powerful, but as an example: the two dueling demon lords it spawned aren’t fighting for power or honor; this is a domestic dispute between two extremely intimate (succubus intestines can do what? Why? WHY?) supernaturally-dickish immortals who have been emotionally abusing each other for a thousand years, and they’re airing all their dirty laundry. Take sides if you dare.

Ring of mind shielding: Also shields you from anything uncomfortable; you do not gain xp. (Yeah yours is better)

Ring of mind shielding (extremely racist): you can’t see elves’ faces now. you’re welcome.

Portable hole: It’s soft, meaty, and contains multiple (always closed) giant sphincters. Sometimes shudders. Otherwise functions normally. So far.

Wand of wishes, but gives you what you actually want right now.

Yeah, you need a bridge, but you’re fatigued, so on some level what you really want is a hot bath and a warm bed; maybe some soup.

But people can see your footsteps cartoon style

Wand of Wonder What This Does

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

Ring of (Logical) Invisibility v2. Makes you invisible except for your eye balls so that they can absorb light. You may now see but you appear as a pair of floating eyeballs.

Worst thing ever, don’t even want it. Would ruin my life

Ring of minor invisibility - The ring is invisible, and only makes your body invisible, not any of your stuff

Sword of charisma: But it attracts bugs for some reason.

Amulet of protection: Stops heals too.

Boots of speed: Brakes not included.

Wand of light: Slightly radioactive.

Potion of restoration: Removes buffs as well, kills undead.

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

There was an older barbarian subclass that was immune to magic including beneficial magic. It was dumb and wonderful

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

I gifted my party a sapient dagger. It was really good too. It was a 1d6 but let you attack again, but rolling a 5 or less on the die makes you insane because the dagger insults the user so badly for missing. If it happened 12 times, the character died. They used it from level 3 or 4 through the end of the campaign at level 18, since there was no cap on how often you could attack again.

It is I Vincenzo The Dragon Smiter, prepare to die!

Donk.