Favorite movie of all time?

So in my American History/Lit class my professor had us introduce ourselves, say our hometown, major, etc. and then had us share our favorite movie of all time and explain why. Without even thinking I would've replied "It's A Wonderful Life." But my professor went first! and I definitely didn't want to come off as a suck-up on the first day of class! I was the third person to go, so I had to think quickly.
I really wanted to say "Heavyweights," it's a hilarious movie! Basically a bunch of fat kids are sent to fat camp and a new director takes over and tries to starve and work the kids out to exhaustion. My favorite line was when Ben Stiller (the evil director) says, "Attention Campers! Lunch today has been canceled due to lack of hustle. Deal with it." Sooo funny...
But since I panicked, I said "The Sandlot." It's a neutral pick, not a chick flick, not a dude movie. It's true though it was one of my favorites but definitely not of all time.
Next on my list would've been "Ferris Bueller's Day Off,""Little Giants" or "The Santa Clause." Is it weird that all these movies I pick are from my childhood?

Chick Flicks on my list would probably include, Love Actually, The Notebook, Titanic, The Wedding Planner, and Chicago.

What movies would be on your list? If you were in my position what would you have told the class? Any movies you recommend I add to my collection?