Anything from the original Godfather. In addition to being the most absorbing, most thrilling, best scripted, best acted and (all-around) greatest film of all time, Coppola's 1972 classic is the Zen MASTER of classic lines.
"I'm gonna make him an offer he can't refuse", "Luca Brasi sleeps with the fishes", "Never take sides against the family", "You need a wartime consigliere", "Leave the gun; take the canoly"...the list is endless.
I also have a spot in my heart for "They may take our lives, but they'll never take OUR FREEDOM!" from Braveheart, and "Zed's dead, baby; Zed's dead" from Pulp Fiction.
Oh, how could I forget to mention something from Caddyshack. That movie is the comedy Bible.
"When you buy a hat like this I bet it comes with a free bowl of soup...but it looks good on you though!"
"You'll get nothing and like it"
"This steak is so fresh it still has the marks of the jockey's whip on it"
"Hey, everybody. We're all gonna get laid!"
"So I've got that going for me...which is nice".