Hmmm a tough one as theres so much stuff out there.

If you are asking standard Keyframe stuff then its gotta be Pixar for all their stuff and also PDI Dreamworks for the first Shrek movie

But for mocap stuff with the overall cg stuff I would say Robot for their killer opening sequence for Onimusha 3, Outstanding to say the least, and of course Weta for the Gollum stuff although he was keyed here and there too.

_J