Favorite "Classic" Movies

A digression from the year-in-review, here's another challenge to list favorite classic movies. For the purposes of this list, "classic" is defined as "movies that came out before I was born."

A Night at the Opera
An Affair to Remember
Arsenic and Old Lace
Casablanca
Gone with the Wind
Horse Feathers
It's a Wonderful Life
Monkey Business
North by Northwest
Notorious
Rio Bravo
Roman Holiday
Sabrina
Shaft
The Big Sleep
The Great Escape
The Sons of Katie Elder
The Sound of Music
The Wizard of Oz
Three Days of the Condor (oops, this came out after I was born)
To Kill a Mockingbird
Yours, Mine and Ours