VG Cats + Sephiroth... It doesn't get any better than that!
(I used to use Super Effective avatars of Red. Yeah, I'm a real advocate for that cartoonist.)
That artist used to be great, back before he started stealing two thirds of his jokes from other webcomics.
My avatar represents Tetris Attack, the second best puzzle game ever, and for a long time my favorite. I have it on a rotation, using three different versions (one is actual ripped sprites from the game, one is cleanly photoshopped, and one is shopped to have lots of effects). I don't play the game much anymore, but even now, it's my favorite to use as an obsession, for avatars, etc.