The CC is so vast it's hard to just name a few. You can't go wrong with anything directed by Bergman, Truffaut, Godard, Kurosawa, or Bunuel. For someone who is just starting out with the collection I'd recommend Breathless, The 400 Blows, The Seventh Seal, Ivan's Childhood, The Discreet Charm of the Bourgeoisie, or High and Low. Those are all good starting points.