Op 22, its wikid. The only thing is that the slow movement isn't great imo and that detracts from the rest. Its also really fun to play.
Good choice brew, WIKID is right, it's farking hard! But the slow movement is beautiful! He hardly ever writes a melody like that, but when he does...

Anyway my favorite (right now anyway, but I've felt this way for a long time) is...
Sonata in d minor op.31#2, "Tempest"
Somewhere there is a poll that asks you to vote for your 3 favorite Beethoven Sonatas, don't remember where it is.....