Out of the main characters probably Butters, he's adorable and funny at the same time because he is so naive. Out of secondary characters, probably Clyde. I don't know why but I just do.

Oh and Chef before he died of course.

I'm not quite sure, although I'm not really a fan of Randy Marsh. I feel like he's become a bad attempt to replace Chef, and Creme Fraiche sort of confirms that. Oh and that other cop, whatever his name is the Irish one that was searching for prostitutes. Totally replaced Barbrady for no reason.