The Thing is pretty much the definitive study of paranoia and horror. But then I would recommend it for any movie night, even a girl's rom-com.

The Shining is fairly spectacularly excellent and is a great second choice.

I've never seen The Descent because the trailers never grabbed me. That said it was written and directed by the same chap who made Dog Soldiers (Which is also epic and should go on the list, though it's very comedy-heavy) which is a big point in its favor.