My first handle ever was Seven or Se7en, I used it with some online games and when skateboarding I often tagged it on my board with a marker.
My second handle was/is (still in use but on other forums) Jump in the fire, a song from the band Metallica which I both like a lot. Often used is JITF for short.
And my current one Schizma, is a Hardcore/Punk band from Poland. My Polish is pretty much zero, but they have several songs in English. And I like those a lot too. Plus I liked the name Schizma when I read it.