Her role as Wendy Torrance in The Shining is amongst my all time favorite performances by an actor.
Obviously, I don't think it justifies her treatment at the hands of Kubrick, but the fact remains that it was an extremely impactful performance to me.
I've never been one for parasocial relationships or making assumptions about the private lives and personalities of famous people, but I could never help but think Shelley Duvall seemed like she'd be a very pleasant person to be around.