If you like Robert Duvall and haven’t seen THX 1138, I would highly recommend checking it out. Also has a great performance by Donald Pleasance.
Duvall had a small part in Slingblade, and a small part in which he is nearly unrecognizable in The Road, one of the darkest movies ever but excellent.
Outside Lonesome Dove, my favorite Duvall
character is The Great Santini.