I have 2 4 usernames actually. (Last two are hardly used.)
First is Simskiller my primary, which was created after watching a few Episodes of Strangerhood by roosterteeth (Which I watched before Red vs Blue as that looked boring to me at the time (I believe it was episode 52 they were at when I did start watching), and wanting to comment/post on the forum I had to think of an appropriate username. I played the Sims as well and I killed them... a lot. Mostly with fire. Hence Simskiller was born, with my Xbox motto being "Sims+fire=SMORES!" (Even though I don't own a Xbox and it's my Games for Windows live motto which is basically Xbox on the PC).
I add 101 at the end as my lego username when I was a kid was kid101. I made that when I was 8 or nine.
(Used basically every bloody where I can)
Second is Lokikron, which is a combination of a Norse God (Norse mythology rules) and the misspelling of the name of Conan's god in Conan the Barbarian, due to Arnold. (Used in mmorpg's)
Third is lokiandosiris (Youtube and second email), combination of Norse and egyptian mythology/ It's the name of The Order's Mothership in Freelancer.
and Forth is Aurius Fenrir a name a friend made up for my character in a story he wrote using other peoples characters. I used it in APB beta and EVE and that's it.