Mine was an easy choice :- Chris_M1BIK
M1BIK added to make it unique, as noone else was likely to use my ham radio callsign in their PSN ID - i actually wanted it to be simply M1BIK, but the f*ck up of a registration system wouldn't allow it. I seem to remember it somehow (and it defies belief) that the letter-number combination somehow conflicted with the profanity filter, but passed when appended to my name.
Weirdness - mysteries of the universe and all that stuff