Ok This thread reminded me of this old bit...
Yeah guys like Blob and Shit-Head would be the worst. There wouldn't be a toilet left after Blob. Radioactive Man would be bad, but I'm not sure he even eats or uses a toilet. Absorbing Man I'll bet has bad habits too. Wolverine would probably leave hair everywhere.
Joker I'm not so sure because some incarnations seem like they might keep things neat like that, I mean he does walk around in an expensive suit at times. Also, he is unpredictable. You think he's going to leave a mess, so he leaves it nice and clean - or then again maybe he leaves a dead body in there or some joker venom wipe on the toilet seat.