My first username ever was simon_003. It was the first e-mail address I ever registered, I think. I registered it 7 years ago in 2 months on hotmail. I was nine years old!! I still use it occasionally, although I much prefer Gmail. I got this address because my birthday is on the third day of the third month, and because I mistyped simon_0303 into simon_003.
My current username was made when I started a band in 7th grade with an old friend of mine. He always said that I had a strong belief that our band would go far and never end. I said I simply had Aced Faith within me. From there, my username became Ace Faith. I use it for mostly everything, except my emails.
Another username I occasionally use (not on the Temp) is Qasdelo. It was an idea for UI I scrapped months ago. I called it Qasdelo because QASDE spells out a U on the Keyboard, and LO spells out I, hence "UI".