The Staff of Insect Plague: a gnarled wooden staff standing at 6 feet tall, topped with a smooth green stone. It can be used once per day to summon a swarm of butterflies that engulf a 20-ft cube. No damage dealt—but it is quite pretty.
The Pocket of Holding: a small pocket that can be sewn into any article of clothing. Holds up to 80 pounds of whatever will fit through the opening.
The Feather of Heavy Fall: though light as a feather to its holder, the object itself weighs as much as a kilogram of steel. It will also double your own weight, so try not to trip or walk off a cliff without noticing, because you’ll be taking 2x damage from any fall.
A Hunk of Coal: a hunk of coal that gives a off a faint magical aura. You’re sure it has some kind of arcane properties. That’s what Detect Magic says, right? So it must, right?
Wit for Dummies: you’ve heard of Sparring and you’ve heard of Magic, now introducing Wit for Dummies! Once per day, this small leather-bound book will allow any non-bard to cast either Vicious Mockery or Cutting Words.
Kitty Biscuits: a metal tin of 12 small biscuits. If fed to a cat/cat-like creature, it will grant advantage on animal handling checks (or persuasion checks) for 10 minutes. Also, will inexplicably attract all felines towards you in a 30-ft radius.
The Ring of Purification and Refreshment: instantly turns any beverage the wearer holds into sparkling water (including but not limited to: beer, still water, poison, healing potions)
Concept: a D&D campaign where every party member has been co-opted or replaced by some sort of hostile intelligence; e.g., the fighter has been possessed by a ghost, the wizard is being mind-controlled by her sapient magic ring, the rogue is actually a shapeshifting blob-monster who devoured the original and stole her form and memories, and so forth. Each of them is totally unaware of the others, and believes itself to be the only monster in a group of unwitting human adventurers.
The warlock has been infested by a demonic fungus; her ridiculous hat conceals the giant mushroom growing from the top of her head.
The barbarian is a lizardman who fell victim to a botched reincarnation spell and regenerated as a human.
The druid was actually killed weeks before the party met, and is being expertly impersonated by three dire raccoons in a trenchcoat.
No one knows that the bard’s deal is; she seems perfectly normal to every physical and supernatural test, but pings to detect aberration.