What I love about Noir is that nobody ever really gets away with anything. If you're in a Noir movie and you think you have, you're in for an unpleasant surprise. There's some detail you've forgotten that comes back to haunt you. If you get acquitted of a crime you committed, you'll be convicted of a crime you didn't commit.
Noir scenes I love:
*Double Indemnity:* Edward G. Robinson's speech on, of all things, actuarial tables and suicide. Robinson telling Fred McMurray he'll never make the elevator, and being right. McMurray telling Robinson "I love you, too."
*The Maltese Falcon:* Peter Lorre mildly asking for his gun back, then turning it on Bogart and saying (for a second time) that he intends to search Bogart's offices.