Most of my accounts are named "fn" -- my initials. When I was living in SF a housemate gave me a NeXT slab, and I named it "id" and created an account on it named "self" -- both objective C keywords. "self" is also my icb nick.

I still go by "fn" on most accounts I have, though there are a few random ones with names like "lambda" (from lambda calculus).