Avatar (James Cameron, John Refoua, Stephen Rivkin)
Those 2.5 hours just fly by, thanks largely to the editors' expert pace-setting and smartly-applied scene cross-cutting. No one does action better than Cameron.
Transitioning smoothly between various types of footage, the smart editing of this documentary constantly has you wanting to see what happens next.
The Hurt Locker (Chris Innis, Bob Murawski)
Suspense and tension is brilliantly evoked by the gradual build from relaxed scene-setting cuts to frantic split-second cuts. Tick tick tick...
No shot lasts longer than it needs to be, nor gets cut off prematurely. Each scene is paced such that the lengthy narrative flows efficiently without feeling rushed.
Star Trek (Maryann Brandon, Mary Jo Markey)
The action pieces are put together excellently. They also manage to afford adequate screen time and closeups to all of the many characters.
Just missed: Up in the Air, (500) Days of Summer, District 9.