Shindlers list is excellent. Shawshank Redemption most definitely in the top 3 but i wouldn't class Saving Private Ryan or Departed in there. One flew over the cuckoos nest or any of The Godfathers would be up there for me. The Pianist, Band of Brothers & Platoon would be other great war movies.
You gotta love the opening scenes from Private Ryan though, absolute class! I was lucky enough to get to be an extra on it, believe me even when your there certain aspects of it looked real when the scenes were being filmed.