Hmm well I began my online gaming on Xbox 360 first, and my username was "Buddie808" Buddie because my friends always called me that, and 808 because of the State I live in, the area code is 808.
During a match of Gears of War, someone felt so inclined to inform me that my username was un-original because I had numbers in it, and he kept going on about it, and it actually upset me.
A few days later, It really got to me, and I finally caved and changed my username to... Go Buddie Go. It was completely random, and that name stuck with me, especially during clutch matches I would win, and my teammates would shout "Go Buddie Go, GOOO!" Lol.
Finally got me a PS3, and so of course it's only natural I stick with the same username.
Mine's a little outta left field:
GEMINI - from a game I played and really enjoyed back on the N64 called Jet Force Gemini
Vice - a character I really liked out of the fighting game Capcom vs. SNK 2: Fight for the Millenium (her name was Vice and I liked her demeanor and fighting style)