I'm a fan of a lot of classics that few have seen.
Philadelphia Story: Carey Grant, Katherine Hepburn, Jimmy Stewart - brilliant dialogue all around.
To Have & Have Not: Bogart & Bacall doing Hemingway, good stuff
basically you can't go wrong with anything with Grant, Bogart, Katherine or Audrey Hepburn
Also, any of the Marx Bros. movies
oh yeah, and if you still haven't seen Casablanca or Citizen Kane, stop whatever you are doing and put it at the top of your Netflix cue right now