I’ve got a few, many of them are from my science-fantasy campaign or my UVG campaign:
A wooden box with a small talisman in it. If the box is closed when the talisman is not inside of it anything currently inside of the box switches places with the talisman.
The Hell Gun, a laser weapon forged by the humanoid-hating AIs inhabiting the dimension of Tartarus. It has a fleshy appearance. When held in the hand, the eye at the front of the weapon opens up and scans the area in front of the weapon, while mentally probing the user. It then fires at whatever target the user hates the most. The user can roll a check to attempt to control their emotions and select the target instead.
The Astrolabe, a sealed transparent sphere containing a swarm of nanomachines. Through unknown means, the nanomachines show a continuously updated scale model of the current star system. The scale goes down to tracking the position of every starship in a system, although it does not render details of the specific ships.
Electrified Spear, a commonly used anti-vome weapon. The spear head is hooked up to a scavenged battery, which allows it to fry electronics.
Xerox Machine, a wonder of the ancient world. It can copy an entire spell book in a matter of minutes, threatening to disrupt the balance of magical power among wizard factions.
A gift from your estranged uncle Zanthar
Wooden puppet that attempts to do one mundane task per tooth deposited through a door in it’s hollow skull. New tasks will only be performed in exchange of new teeth. The magic can be fooled but at risk of the new task going afoul with the old.
The Demon-Devourer(d8; d10 vs demons, bulky)
Curved two-handed greatsword. A golden blade ornamented with electric blue script in a fel language. The sword is covered in the blasphemous names of the demons it has devoured. Critical damage against a demon consumes and imprisons them, and their name immediately appears upon the weapon.
Make a WIL save upon devouring. Save with advantage if you know the demon’s true name. On a fail, the script violently explodes off of the blade for 1d12 damage to anyone within 100 feet and all imprisoned demons are unleashed back into the world. Wielder is deprived until another demon is devoured.
Well traveled - tin of dried fruits
A tin filled with an assortments of bite size dried fruits. On consumption you speak a different language that is not native to you for 10 minutes.
The Spear of Tiny Des
Long before the river carved it’s way to the sea, the Great Pixie Lord Tiny Des was convinced that they were the greatest spear fighter to ever live. Frustrated at not being able to fight larger people, they spent their kingdom’s fortune to create a spear that would transform opponents to their own size.
This ornate spear is about 2 inches long. When the wielder takes hold of it they immediately change sizes to be completely proportional to the spear as if it were 6 feet long. Losing contact with spear causes the wielder to instantly regain their former dimensions.
Oh, I really like the idea of making some sort of collaborative item deck.
Especially if we could format it for printing at home, you can easily make a good deck by cutting out cards and putting them in a sleeve with some sort of trading card.
I have a big deck of index cards with magic items. I make sure to draw every one even though I’m not a great artist. I think it’s so cool if you can hand a card to a player once they find an item, and they get something interesting to look at.
Only problem is since getting into the OSR my magic items are now mostly a sentence or two and an index card is a little too big!
Hoberdy’s Lantern A dried, hollowed out green gourd with a wick that will continue to burn without any apparent fuel. Instantly snuffs out in the presence of restless spirits.
Soup’s Bowl A large, intact black tortoise shell. Discoloration on the interior suggests it’s been used as messware. If the shell is filled with soup or stew, a baby tortoise emerges from the broth. He responds only to the name “Soup,” and is surprisingly intelligent. Any meal eaten in the presence of Soup is particularly delicious and filling. Anyone who attempts to harm Soup will find themselves unable to keep food down for the next week.
Door Paste
A toothpaste-esq tube, the contents can be smeared upon a wall in the shape of a door (any size so long as you have enough paste) which manifest temporarily allowing passage through the wall (it fades with time).