A few that haven't been mentioned yet.
Crank 2- the shotgun up the ass
Last Man Standing
The last run in Wanted
Jesse Ventura flattening a forest in Predator
Arnold taking the minigun to the cops in Terminator 2
The quick and the dead had a few good shots too.
Dude with the most awesome gun moments- Chow Yun Fat. All Hail.
Grand Poobah of T.W.A.T.