I can second this recommendation. The movie is both very intense and subtle.

Catacombs or The Descent

Another recommendation for Sinister from me. My wife and I watched it late at night, and we had to watch two episodes of The Big Bang Theory afterwards, just to get it out of our system, before we dared go to bed.

kinda surprised nobody mentioned rosemary's baby or jaws yet
or is it because they arent that scary any more ?

the excorcist definitley still is disturbing

Yes, The Conjuring is absolutely fantastic. I highly recommend it. It is awesome in every way.

Hehe...yeah, it seems apart from the Last Airbender our tastes in movie do align quite well. :P

I would also recommend another movie Mama if you haven't seen it yet, also really well done and the story is quite good for this genre. Here is the original short on which the feature length movie is based.

MAMA the original short film

Hmm, it might be, I wouldn't know. What I do know is that if someone does plan to watch The Exorcist, I recommend that they stay far away from the Director's Cut. It's the only version I've seen, and I turned it off after 45 minutes because it was boring as hell. I've heard people who have seen both versions say the same thing, stay away from the Director's Cut.

Mama was a good movie until the end. No spoilers, but the endong killed the movie for me.

Yeah, Mama was pretty good.

Oh, you know what movie I thought was scary and many people didn't like? Signs. I liked it b/c it was the whole "bump in the dark" scary, not "chased by monsters/psychos" scary.

I like The Descent a lot, though it suffers in home viewing - in a movie theater, with proper volume, it's intense and scary.

Catacombs is a movie I enjoyed fairly well, although it's silly. I appreciated it in part for exactly what turned a lot of people off - there's a weird stretch in the middle which is, pretty much, just black, because in fact it would have been, well, just black. There's relatively little of that "lit in red meaning dark" or "lit in blue meaning dark" stuff.

Also: Catacombs features Pink, and stars Shannyn Sossamon.

Try to avoid The Cavern, which is not only terrible but also incoherent and mean-spirited, and The Cave, which is OK I guess but rather bland. There were a lot of spelunky movies around then.

I thought it was a brave choice, very divisive but it did make sense to me. I also totally understand though if it ruined the experience for some folks as well.

I ubderstand why the ending had to be like it was, just didn't like it ;-)

Older but i like them:
Martyrs
I spit on your grave
The hills have eyes