Ooh, that can be a prettt long list:
Valve - for the absolutely fantastic Half-Life series, L4D, Counter-Strike and other Source awesomeness
Neversoft - for Guitar Hero 3
Bungie - people give them a lot of crap but the Halo formula is really really good
Blizzard - for turning people into "mindless zombies"... scratch that. For all the hours I've spent playing Wow and Warcraft 3
Rockstar - self-explanatory
Capcom - for Dead Rising
Treyarch - okay, this one is kind of stupid, all they do is reskin previous Cod games but the last 3 missions of COD 3 and Nazi Zombies are really good.
Ea Sports - for NHL 09
Codemasters - for Toca Race Driver and Dirt
And, to top it all off:
Infinity Ward - for making 3 of my favorite videogames of all time, making me an FPS fan and standing up against Activision's idea of adding a subsribtion service (like in most MMORPGs)to Cod multiplayer.