The Mist. Loved the rest of it (except for the mischaracterization of Christians at the grocery store), but I hated that ending soooo much.
Yep, that's Stephen King, all right.
"The Mist" was a great adaptation of, IMO, one of his best shorter stories...until that ending. It was like a punch in the stomach. After seeing it, we were depressed all the way home.