Some of my favourites:
Sound of Music
Mary Poppins (I have GOT to see "Saving Mr. Banks", though Tom Hanks looks nothing whatsoever like Walt Disney, whom I used to see nearly every Sunday evening as he introduced the latest enstallment of "Walt Disney Presents".
Casablanca
African Queen
Captains Courageous
Adam's Rib (IMO, the best Tracey/Hepburn film of them all!)
Guess Who's Coming to Dinner? (A groundbreaker, for its time!)
No one has mentioned Westerns so far, but I LOVE Rio Bravo! John Wayne, Dean Martin. Walter Brennan, and Ricky Nelson (who sings with Deano in a great tension-breaker scene part way through the film.)
Ladyhawke - I have the VCR cassette. Last time it was on TV, I said, "OKay, I'll watch a few minuites of it." I would up watching the WHOLE DARN FILM commercial breaks and all! It's a great medieval fantasy, and both Rutger Hauer and his horse, Goliath, are gorgeous to look at.
Ben Hur
Rear Window
Most of Mel Brooks's movies, but especially Spaceballs, and Robin Hood- Men in Tights.
Titanic
Avatar
In her last years, Hepburn did a great little TV movie called "The Man Upstairs". It was one of her last films, but it was, IMO, a real gem. Ryan O'Neal plays an escaped convict who takes refuge in her attic. Before he knows it, Hepburn's octogenarian character has him wrapped around her little finger! I'd love to see it again sometime!
Films I feel are over-rated, and don't much care for:
2001: A Space Odyssey
Gone With the Wind The cinematography is breathtaking, but Miz Scarlett and I will never be friends.
Butch Cassidy and the Sundance Kid My brother loved it but it did nothing for me. Guess it's mainly a guy film
Clint Eastwood's Man with No Name movies - see above!
Citizen Kane - well, if I ever get to see the film from start to finish I might change my mind, but my most recent viewing, which covered all but the opening scenes, left me going "HUH??"