We all may have other favorite characters, but we can't deny that Kenny is the nicest fella in town. Like, he is literally the definition of "nice guy".
I personally rank "Major Boobage" very high, though the episodes from season 6 where his soul is trapped in Cartman's body are among my all-time favorites, and don't get me started on his Mysterion moments!! probably his most epic.
BTW is it mentioned in an episode his birthday date?