Celebrating my birthday caused a one day delay but I am back up now.
Buried is literally a one man show with Ryan Reynolds waking up in a coffin. He has a cell phone and a lighter but not much else. He is a contractor working in the middle east who has been captured and buried by the enemy. He only has so much power left on his phone and air in the coffin. Like Open Water, this is a "could actually happen" situation that is intense and claustrophobic.
I think Reynolds does a great job of selling the panic and the intelligence the protagonist needs to exhibit to make the plight realistic but not necessarily fatalistic. I don't want to give too much away, and some people would claim this isn't even horror but I defy you to find me a more frightening scenario to deal with.