Username, honestly, not so much.
I'm not going to say mine's good. It's awful, but it's what I use for everything.
Best: Vagrant was pretty cool. ABC, 1337endo, Ekiushi's fun to say.
Worst: Frogger...seriously, it sucks. Bliss: too many people think you're a girl, anything with numbers, underscores, or surrounded by any of the following: