People on Sunday (1929) - Robert Siodmak & Edgar G. Ulmer 

Considered a landmark of avant-garde cinema I can't honestly understand why. The film is a somewhat straight narrative showing a few Berlin people enjoying their day off, and juxtaposing that with their weekday lives. I'll admit a lot was lost on me because I wasn't able to see the BFI DVD, which left me with a bad transfer and French intertitles. The script was written by Billy Wilder, and nearly everyone involved in the making of the film went on to careers in Hollywood. The cinematography is largely excellent encompassing a few early wide angle compositions and almost entirely shot outdoors.