Fortnite - Comically Large Player Trap
This item would allow you to set a trap on chests and if an enemy opens the chest the trap snaps and damages them and applying a slow for a couple of seconds.
This would create an interesting dynamic as enemies would easily get enticed by the opportunity for extra loot & xp. It would also be possible to react in time and jump out the way, but players would likely forget as most chests aren't a trap.
The reason I really like this idea is I think it fits in perfectly with the goofy items and vibes that Fortnite likes to create with limited items and weapons.