Valve, for making the best online shooter ever, two of the best shooters ever, and the best shooter stories ever.
Relic, for bringing true originality to the RTS table, with such games as Impossible Creatures (at least they tried something new), Dawn of War (WAAAAAAAAAAAAAGH!), and Company of Heroes (very awesome game).
Monolith, for giving us such goofy titles as No One Lives Forever 1 & 2, and for the slow-mo mayhem that is FEAR.
Rockstar, for the Max Payne series, the inventors of bullet-time, and some truly epic shootouts.
Epic, for Unreal Tournament 99 (my personal favorite Tourny), and my first gaming experience ever, Jazz Jackrabbit.