Magic sword of infinite sharpness.

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

Headband of miner intellect:

• Forged by a dwarven artificer who lost too many colleagues due to their lax attitude around safety.

• Anyone wearing this headband becomes aware of the quality of air and props for whatever tunnel they’re currently in.

• Wearers possess an intrusive urge to find proper protective equipment before attempting a task.

Bag of Communal Holding

Content is shared with all other bags of communal holding in existence. Sometimes retrieving objects involves awkward hand contact if someone else is using their bag at the same time.

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

Axe with increased crit range (both sides)

Flaming sword (no off switch; do not keep near oil, pa}er, etc.

Shock arrows with electrical damage, stun on crit, compulsion to say some wsgelord shit next time youre talking to a new person each time you use one (non-stacking)

Bag of Storing, a bag of holding that doesn’t mitigate the weight of the items within.

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

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).

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.

Immovable Rod:

• Not actually a magical rod.

• Actually just a bloke called Roderick, or Rodney, or something to that effect.

• Won’t move out of your way.

• Not even if you ask politely.

I have two I will be using in my next campaign:

Ring of attunement: Provides 1 extra attunement slot. (Requires attunement)

Event Staff: This staff allows the wielder to gain unquestioned entry into any “employees only” areas or zones otherwise off-limits to the public. Anyone (including actual staff or other officials) who sees the wielder in one of these areas will assume they are a known employee or other official who is granted special access to the area. Unfortunately, they will all also view the wielder as the least competent and least trustworthy employee or official with the organization. Any actions taken in the area are likely to be closely watched and highly scrutinized by any observer who would know better.

ETA: One from the current campaign in which I am a player character. Our DM thought of this one:

Bullet of Healing:

This magical bullet can be loaded into any firearm. Whomever is shot by this bullet first receives 1d6 piercing damage followed by 1d10 healing. If the initial damage causes recipient’s HP to fall below 0 before the bullet’s healing effects begin, they will fall unconscious and will not gain any healing effect from the bullet. Instead, one death save is automatically passed.

Sir Mix-a-Lot (unrelated) is a traveling potion salesman who shows up for my party at suspiciously specific times, and generally has discounted potions specifically tailored for whatever they happen to be doing at the time. For example, if they need to be really strong, he’ll have a bottle of Sir Flex-a-Lot’s Magical Muscle Maximizer, which does increase the strength of one’s muscles, but not of their bones or connective tissue (it was designed to be used only in bodybuilding competitions), so whenever the drinker does a STR check, they must also make a CON saving throw to avoid breaking a bone or tendon. Need to decipher an ancient text? Try Sir Scripts-a-Lot’s Polyglottal-in-a-bottle, which will let you read unknown languages, but also comprehend all unknown languages, even those of the plants and animals around you, making it very difficult to concentrate on any one thing. (inspired by https://www.smbc-comics.com/comic/springtime)

Collar of Commerece: +10 barter and gives canines the ability to understand commerece and run businesses, aflicts them with knowledge of economic exploitation and inequal power dynamics

The All Severing blade. It cuts through anything you want it to cut. And also your own hands. Make sure to have a healer on standby and use plenty of painkillers.

Wand of wishes. It’s great, but it will respond to any speaker in the vicinity