No one is really talking classical Hollywood here, so I'm gonna go ahead and pimp some of the greats (skipping Hitchcock and Welles, since everybody knows them).
Samuel Fuller, Nicholas Ray, Frank Tashlin, John Ford, Anthony Mann, Howard Hawks, Billy Wilder, Preston Sturges, Jacques Tourneur, John Huston, Otto Preminger, Jules Dassin, Vincente Minnelli, Douglas Sirk, Fritz Lang, Elia Kazan, Andre de Toth, Joseph H. Lewis, Robert Aldrich, and of course, early Stanley Kubrick (can't believe no one's mentioned him -- IMHO, his best stuff is the one-two punch from '56 and '57, The Killing and Paths of Glory.
This is just a sampling, but check out anything you can get your hands on by the above directors if you want to delve into the treasures of old-school Hollywood.