Oh man, I have so many. Absolute favorites are in bold.
Sabrina - Audrey Hepburn, Humphrey Bogart
My Fair Lady - Audrey Hepburn, Rex Harrison
Citizen Kane - Orson Welles
The Odd Couple - Jack Lemmon, Walter Matthau
The Apartment - Jack Lemmon
How To Steal A Million - Audrey Hepburn, Peter O'Toole
Dr. Strangelove, or: How I Learned To Stop Worrying and Love the Bomb - Peter Sellers
Rear Window - Jimmy Stewart, Grace Kelly
Singin' In The Rain - Gene Kelly, Debbie Reynolds, Donald O'Connor
Yankee Doodle Dandy - James Cagney
His Girl Friday - Cary Grant, Rosalind Russell
Charade - Audrey Hepburn, Cary Grant
Arsenic and Old Lace - Cary Grant
Harvey - Jimmy Stewart