Teenage Mutant Ninja Turtles (1990): When Splinter and Danny are talking, and Splinter asks about his parents. And gives a line that's become even more powerful since I lost my dad last year - "All fathers care for their sons."
Waking Life: Really this whole movie, because it's just scene after scene of interesting ideas and great dialogue, which, thanks to the way the movie is built, doesn't need to be super-connected. But I guess the scene i keep coming back to is when Wiley is with an old man in what looks like a bar. It ends with a powerful line: "Which is the most dominant human trait - fear? Or laziness?"
Johnny Mnemonic: "I! WANT! ROOM SERVICE!" Just a great delivery and a real show of how he's gotten to the end of his rope.
Midnight in Paris: Hemingway's introductory scene.
Casablanca: The ending especially, but also La Marseillaise vs. the Nazi anthem.
The Third Man: The Merry-Go-Round scene. It's a chilling look into villainy, and the obvious fact that Harry Lime was not always the monster he is in the film - because he can't look at his victims as people. It's why The Lives of Harry Lime worked as a radio show.