The Third Man (Orson Welles spy thing), City Lights (the Chaplin classic about the blind flower girl), French films which follow on from each other Jean de Florette followed by the 'sequel' Manon des Sources, Dr Zhivago (the David Lean film), Fiddler on the Roof (the film with Topol), 2001 A Space Odyssey. They are all 'classics'.
Gettysburg Fun fact: The older looking captain to Cahmberlain's left (to the right of the screen) was the Adjutant General of the Pennsylvania National Guard. He was a major general who they asked to be an extra in appreciation of all the PA ARNG did to support the movie.
Star Wars (And I still call this #1)
And the greatest motivational speech of all time....