Mario - Still like this series, must get around to playing Super Mario Galaxy.
Sonic - Used to like him, back when it was still the 90s. I played Sonic Heroes though, and thought it sucked big fat donkey balls. Never again.
Halo - Never played any of them.
Doom - Still play this sometimes using PrBoom, ZDoom, or Chocolate Doom.
Final Fantasy - Promised myself I'd never buy Final Fantasy X, then bought it and spent over 100 hours playing it. Then bought Final Fantasy XII, and spent over 200 hours playing it. I'm getting Final Fantasy XIII, time to stop deluding myself.
Pac-Man - Wakka, wakka, wakka, wakka, wakka. Still my smoke test for SDLMAME, and fun too.