Depends whether you are talking about single player or multiplayer.
If we're talking about single player, then there are many candidates. Dafe, ChezDa, Noweb, Kamiko, Dark_Energy, Nuthug, etc. Singleplayer is all about aesthetic appeal.
If we're talking about multiplayer, it depends on the mod.
If we are talking about "multiplayer in general", i have to say TIcux - for sheer versatility. He has won more multiplayer competitions than anyone else, and that says something.
Each popular mod also has it's recognized top players, whom i won't list in fear of leaving some out :P
