Film score
What makes this a great movie for me is the haunting (and very beautiful) score by Ennio Morricone. Its not the only thing I like about the movie, the style of direction (Leonne) is brilliant.
I first saw this movie in 1980 when I was 15 and was, if you'll pardon the unintentional pun, blown away by it. I still feel that and think its highly underrated