Ok I posted this in another thread but it's really cool. A Mr. Potatohead type key with a face(or skull) as the base cap but with two pegs holes on the side like action figures that attach to a base. Then, you can have masks to put on the key for different looks. A ton of masks even like Zombieface, Awesomeface, a Gasmask, a Vader helmet. Anything you can imagine, and some masks would be super rare while some would be common, but all would be cool. I dunno how molding works, but doubleshot and tripleshot masks would add a ton of flavor.
Also: A Cthulhu keycap. A flatter style one in the same vein as CC skulls and the Gasmask caps. Please oh please on my dirty knees, I want this to happen