Jack Nicholson's intensity on this is amazing. I still get chills every time he yells "You're [GD] right I did!" Nicholson offered to continue to run his dialogue while the camera was taking Tom Cruise shots. Supposedly, every time his intensity was spot on. Pretty damn impressive.
(Also, I love the insertion of the seemingly random "Who's going do it?.... You Lieutenant Weinberg?" Kevin Pollock once said "Whoa! What did my character do to piss you off? Wander in the desert for 40 years?" which is a great line. But that line isn't an accident it's thrown in there to remind us of how flawed Colonel Jessup is. It's subtle, but perfect.)