A long time ago when I was about 10 or 11, I wanted an account on the Popsicles website (I can't remember why; I think it involved games or something). I wanted the name "icecreamman", but I accidentally typed "icecreammac", and it was too late to change it. Ever since, I've chosen icecreammac for every single website I've ever been on (with the exception of my school username, which uses my last name and first and middle initials). It makes it easy to remember, and I've grown to like the name.
I have no idea what I'd change it to; maybe icecreamman, like I intended to from the beginning, but a 21-year-old with that name is a tad creepy.