Jack Nicholson has been in a few really good movies. This is one of his most famous scenes from 1992's A Few Good Men. Tom Cruise actually does a good job as do all the supporting actors, which includes Kevin Bacon, Kiefer Sutherland, and JT Walsh.
In a nutshell, Tom Cruise and Demi Moore are investigating the midnight death of a particular marine by two other marines. They believe Col Jessup (Jack Nicholson) had something to do with it.
Famous for the "You can't handle the truth!" line, I like the rest of the monologue, particularly "And my existence, while grotesque and incomprehensible to you, saves lives."