Collected here are a few rough magic items I jotted down in a notebook last summer.
The sword does an extra 1d4 damage for each opponent you argue with while wielding it. Your opponents must reply to your statements, and you must be wrong about everything you say. The sword also gives its carrier Disadvantage on all Persuasion checks.
A golden toad whose croaking song (like a whale-noise?) requires any who hear it to make a Wisdom save (or a save against mind-control) or be forced to draw nearer to the toad, transfixed.
Originally part of a monster-encounter in a hexcrawl. It was one half a symbiotic relationship with a lake monster. The toad sat on the submerged lake-monster which pretended to be a rock while the toad lured passers-by into the water with its song. Then, the lake monster would drown and eat the mesmerized victims.
Mongoose & Snake Arrows
Mundane arrows or bolts, with arrowheads forged in the shape of either animal. The arrows give their archer Advantage on any shots against their natural prey: Mongoose Arrows provide Adv. against snake-like enemies. Snake Arrows provide Adv. against rodent and bird-like enemies.
When fired, the arrows turn into their respective animal mid-flight, latching onto and attempting to bite/maul the target. Stats as mundane rodent (like a weasel, I guess?) or snake.
Or 1d4 HP, +3 to hit, 1d4 damage.
Flower of Carnage
Pulling off a petal will cause a target's limb to be torn off (can only be done once per wielder of the flower). If a victim of the flower is able to use the flower on someone else, their lost limb can be easily reattached, stitching itself back to the wound with a web of root-like fibers.
Sign of Hospitality
Nail this wooden sign to any door and the door will open to a cozy cottage, sort of like Tiny Hut.
Crown of Silence
No sound can be made within a 100ft. radius of the Crown except when the wearer speaks. This causes 4d6 damage to everyone within earshot (Dex save allowed to clap ones hands over their ears). This can only be done once/round but the act of speaking can be done as a free action or a reaction.
The Crown-Wearer takes damage for every use after the first in a given day.
Vial of the Melted Star
There is a massive irradiated inland sea in the Elflands, full of liquid starlight from a fallen star. This is a vial of that liquid. Fey energies attract the attention of faerie-creatures, normally hidden to all mortals but children. You can see Lay-Lines and easily seek out the Elves' hidden portals to the Lunar Wastes.
If you drink the vial, make a Con save or die. If you succeed you are instantly immunized to all radiation.
(Gnomes, Elves, and other Fey-adjacent folk are unaffected.)
Sword of Regicide
Advantage and +3d8 damage on all attacks against monarchs and people named Reggie. The sword will turn against any wielder that dons a crown, and refuses to harm peasants and civilians.
Chain of Freedom
Broken manacles, usable as a heavy whip or flail. +1 versus all oppressors & advantage on all saves and rolls against being restrained, grappled, paralyzed or held.
Ceases to exist when exposed to sunlight, reappears when the wielder returns to shadows.
Hammer of Salt & Sea
Conjures a massive wave when it strikes a body of water larger than a puddle. Anyone caught in the wave (30ft. wide, 20ft. tall, 20 ft. long?) must make a Dex save or be knocked prone and take 3d6 damage. Once/day.
(The mechanical effect of this spell was mostly stolen from a 5e spell, Tidal Wave.)
Other Magic Items Whose Names I Came Up With But Whose Effects I Still Do Not Know