An object on a floor that allows the Hunter to throw a prop (dead) bunny into it, making a horrific grinding and screeching noise. The input for dead bunnies would be at an angle to allow for dead bunnies thrown from upper floors to make it in.
Any bunny within the same wing (unlimited verticality) will gain madness over time for a brief period ~10 seconds 1 minute-long (or longer). (Credit to Lasinn Vargr for this addition). Adding up to 1 madness bar.
Also the idea of having a bunny gain 1/2 a bar total (from standing) but twice the madness while they're playing dead, but this might be unnecessary.
Any items within the chipped bunny are output onto the floor (making a massive loot pile for bunnies to look through over time), unless they are items used in crafting, in which case they are given to the magician after the match.
I think this would fit the game well enough, and allow for some very nerve-wracking moments for bunnies. Oh, and it wouldn't work for any live bunnies that still have charge.