What is a classic movie most people have seen and you haven't?

In today's world you can certainly find out enough to know whether those movies would do anything for you, if you can avoid having them completely spoiled. Personally, I liked Titanic and Good Will Hunting even though they were mainly pitched to people your age or even younger and I was in my 30's and 40's. Titanic is a story that always moved me any way, the spectacle they produced on the screen enhanced the "big themes" of the tragedy of hubris and the triumph of love. Good Will Hunting has two gorgeous young lovers, a clever screenplay, and Robin Williams at his peak. What more does anyone need?