What type of film?
If you like fighting films i suggest you watch blood and bone. It is a awesome movie with very good fighting.
Perhaps the SAW Series. I cant think of any more films for some reason
If you want comedy go with Superbad or Grandma's Boy, maybe even Waiting. If you want action go with True Romance or Transporter also Boondock Saints is Epic. If you want horror go with the Evil Dead series any of the 3 will do. Drama go with Memento or Cider house rules. If you just want to be blown away with one of those endings that is just insane and great then The Usual Suspects is your choice.
I own over a thousand movies and have watched wayy more then that just let me know what you are in to and I can send you a list of a couple of must see's.