I have three most favorite movies. I cannot separate them or reduce the list to only 1. So here is the list of 3:
1. To Kill a Mockingbird - the perfect film about the South, where I grew up. Sure, I grew up 30 or so years after the events that were portrayed, but not that much had changed. I *knew* all of those characters.
2. Casablanca - the perfect troubled and complex relationship/romance film, with 2 of the best actors ever caught on film: Humphrey Bogart and Ingrid Bergman. As a young adult, my heart was captured by Harrison Ford; but if I were born even 10 years earlier, Bogie would have been my dream boat.
3. Singing in the Rain - There is not a single scene or song and dance number in this movie that is flawed. And the single best solitary guy-dance in all of moviedom belongs to Gene Kelley in the sequence from which the title is taken. I doubt that anyone who has seen this movie would disagree strongly with this pick, and anyone who hasn't seen it - go rent it and fall in love with a musical!
They just don't make'em like they used to. Probably a good thing though. The trees that grow that sort of talent have long since died.

Salon.com
Comments
Celestial Elf - I am thinking of all the Busby Berkely movies, where (it seemed) thousands of girls lined up in precision dance lines and circles, and made like kaleidoscopes. Those were the days! Maybe your London Snowman could adapt the "Singing in the Rain" to "Singing in the Snow." That would be a lot healthier for him.
Vac and Itchris - Recall where Ingrid Bergman starts humming "As Time Goes By" to Sam the piano player? Ah. The humanity! Melting hearts. "Da dee da da da dahhh"
I beloeve I know the lines in Casablanca by heart.