Red.
I mean... wow. After all those smarmy, wimpy trainers that spout many words at you about winning, losing, giving you annoying advice about life, the universe and everything, here comes a guy that says nothing and proceeds to systematically pummel you.
Just because he is pure epicness. You know when that music starts, you're in serious trouble. Even if you have Lv. 100's there is still a chance he'll beat you.
"In America, Red beats you.
In Soviet Russia, Red still beats you."
Although, when you play as Red, then it has to be Blue (sometimes known as Gary Motherf**kin Oak - "Kanto has 8 badges - he has 10".). Again - the music is pretty epic, more epic than Red's unfortunately (since I think GameFreak messed up a little on the HG/SS remix). The FR/LG remix of the Champion theme was superb for a GBA game. ^^