I think Britney is pretty high on there since she is so funny. To tell the truth I hated Kurt for the longest time. He was so annoying and immature for the part of the series I have seen. Still he kind of grew on me in the last episode of this past season.
Still I think I half jokingly and serious about Tina and Mike being my favorite characters. haha They are such quirky little side characters that are fun to watch when they get involved.