I think that Django is probably the best western I've seen. I like it more than the sequel which gets more props (and isn't really a sequel cos it has nothing whatsoever to do with the first one and has a different guy playing Django I think - there are about thirty more sequels along similar lines).
The scene where we find out about the coffin is amazing. Also, Tarantino took the idea for his ear-amputation scene from a similar one in Django.
In terms of Spaghetti westerns (or Paella or whatever), For A Few Dollars More gets my vote.