Mine is basically my name, which is Robby. My little brother (well, he's 20) always called me Robs, but the "z" gives me more credibility on the streets. The "8s" are the truly neat part, though; my birth date is 8-8-88.
I blogged under "Robz888" on a fan site for the TV show "Lost." (The wesbite was darkufo.blogspot.com, and has become an excellent general TV forum called SpoilerTV.) Eventually, this just became my nickname for forums in general.
Nice thread, by the way!