Costner did a great job in that movie too, both as a director and actor. Never liked him much before that, but Open Range more than made up for Waterworld and The Postman.
I agree, I was extremely lukewarm to him before that, but he did it right, there.
Duvall, of course, speaks for himself. My absolute favorite quote is his toast in the hostile bar:
"We'll drink to good health for them that have it coming."