i'd have to say Koss, as it's original (or at least more original than most of the common posters)
some of the others i liked but were ruled out because of unoriginality or partial unoriginality:
Ctb and Ghanghis: both have a historical matching to they're name so they're more of an expected picture rather than
Pin and Chan and Me: we have cartoon pics. while i <3 Gir and naruto + other cartoons, (not so much other cartoons as gir) it's not too original to google your fave cartoon character and edit it to make an avatar
Therese : it's her picture + green what's not to like? oh and it's upside down
others like Carlini, Weiya, Scary pop., Francis, and Raving elmo, Head Void, MPW, brianberu, but no time to dissect the reasons