arlenreyb, arlen, arle, arl, the arltree, karl, Samurai Pizza Karl, RL, etc...
Since this is a nomination thread, and everyone else has really been nominated already, I'll admit that a few of modern algebra's post make me chuckle, what with his dry wit and math-oriented hilarity and all
I'd like to see a proof of that statement. (Get it? proof lol) The more precise term for math-oriented hilarity is terrible, by the way