Peter Dwight at 2010-05-05 09:35:18:

Frailty - http://www.horrorlair.com/movies/scripts/Frailty.pdf

Some considered it too dark. But something about 'killing in the name of...' themes, that has always wow'ed me.

B-Scene Films at 2010-05-05 10:42:29:

http://www.imsdb.com/scripts/What-Lies-Beneath.html

Christian H. at 2010-05-05 11:25:14:

8MM - http://www.dailyscript.com/scripts/eight-millimeter.html

The 9th Gate

http://www.dailyscript.com/scripts/theninthgate.html

Luzid at 2010-05-05 12:18:02:

BURIED.

One of the single most harrowing scripts I've ever read. It literally left me breathless -- as if I were right there in the box with no way out.

Horrifying, thrilling, visceral. I can't recommend it highly enough, nor stop kicking myself for nor having the idea. It's the ultimate contained thriller; I'm not even sure it's possible to get more contained than a coffin.

Robert at 2010-05-05 12:25:09:

"The Lookout" by Scott Frank. The original draft from 1998.

http://www.dailyscript.com/scripts/The-Lookout.pdf

It was considered the best screenplay never made until Frank finally directed it himself in 2007. However I like the '98 version better than the actual film.

James at 2010-05-05 23:47:06:

Anything by Hitchcock.