Cloverfield. With all of the crazy viral marketing (that started way too early) some people were worried whether it could live up to the hype. It COMPLETELY surpassed my expectations, and I went in expecting it to be good in the first place.
Once things pick up and start rolling about 15 minutes in, I didn't relax until the credits started rolling. Yes, they give you a few brief moments to catch your breath, but even then you're still on edge, waiting for the next attack.
I can't imagine this movie being executed in any way other than the hand held approach. They somehow managed to pull off SEVERAL absolutely beautiful shots/camera angles while still fitting into the hand held setting.
The acting and dialog is so natural that it doesn't feel like they're acting a script...at ALL. It's incredibly intense, you're really pulled into the character's corners, and it's filmed wondrously.
Warning: If you get motion sickness easily, you'll probably want to wait 'till this is out on DVD. Other than that...GO SEE THIS MOVIE.