Here's the start of a list.
Battleship Potemkin
Metropolis (Pink Floyd two generations earlier)
The passion of Joan of Arc
Nosfaratu (Dracula)
City lights (Chaplin at his best)
Safety Last (bosshawgs link)
The Birth of a nation (totally racist and not pc, but a very important film)
The phantom of the opera (Lon Chaney invented scary in this one)
Hunchback of Notre Dame (more Chaney)
Add away...