I love little dialogue exchanges between characters, especially ones that give insight to the whole character whilst being engaging. One example would be Watchmen: Veidt: "It doesn't take a genius to see that the world has problems." The Comedian: "No, but it takes a room full of morons to think they're small enough for you to handle." or something small like Spiderman 2: Secretary: "Your wife is on the line, she said she lost her chequebook." Jameson: "Thanks for the good news!" What are your favourite dialogue exchanges?