I'd love to work for either Blizzard or Valve. Blizzard makes the games I really, really love, something about the feel and the lore behind their games is just great. It's fantastical but still very sober and realistic. Valve is pretty much like Jesus to PC gamers because of all the Steam sales, the free DLC, and the continuing support for community-made maps, mods, etc. Both companies make outstanding games and it'd be an honour to work for either of them.