Here’s a simple and probably fun little magic item to throw at your party. The Bag of Wonders.
Here’s your prep as DM. Take 20 index cards. Write a completely random item on each card. I mean anything from a rock, one-foot section of rope, dirty underwear, a dagger, a cursed dagger, a ray gun, hand grenade, evil artifact, anything. Let your imagination go wild. You’ll also want to keep some index cards handy too for adding an interesting item no and then.
Here’s how the Bag of Wonders works. There is more than one Bag of Wonder in the mulitverse. No one knows exactly how many there and where/when they are but they all share the same extradimensional space. There are always 20 items in the bag and these items are constantly changing. In order for a character to remove an item from the bag, they have to place an item in the bag. Characters have no control on what item they remove from the bag. It’s totally random. A character may only place/withdraw one item from the bag each day.
There you go. Have fun with it.