If I may put some plugs for a few films I deem to be essential viewing:
La Fille de l'Eau, which is an early Jean Renoir film showcasing some dazzling cinematography, editing, and visual effects. Remember, this film is from 1926!
Happy Together, Wong Kar Wai's most sublime picture in my opinion. Fantastic character relationships that are told not only through script and acting, but also through the visual delights the director gives us.
Throne of Blood, a Kurosawa film that doesn't quite get the acclaim I think it deserves. A retelling of Macbeth, but even awesomer.
Je, tu, il, elle from Filmspotting's favourite chick Chantal Akerman. This one is tremendously minimalist, but covers some great themes of loneliness and the strange connections that can bind people together, if only temporarily.
Close Encounters of the Third Kind, Steven Spielberg's whimsy and adventurous tale about human-alien contact. Fun, brilliantly filmed.