Christopher Guest has been in charge of some of the funniest movies of the last 50 years, and a big part of what makes them so great is how quotable they are. Waiting for Guffman, Best in Show, A Mighty Wind, For Your Consideration, and Mascots all have lines that I bounce back and forth with my friends all the time, not to mention one movie he didn't direct that might have the most of all, This is Spinal Tap.
