The Machinist

You will not believe your eyes when you see Christian Bale in this film. This goes beyond the weight gain of Robert Deniro in Raging Bull, Jeff Bridges in the Big Lebowski or Rene Zellweger in Bridgit Jones's Diary. Well actually it goes the other way. Bale looks like a skeleton with skin and nothing more. Think "Sloth" in Seven or pictures of WWII concentration camps.
He plays a lonely press operator in a dilapitated factory who cannot and has not slept properly for over a year. Reality beings to be distorted, paranoia sets in. He alienates the few buddies he has at work (in a particularly nasty fashion his coworker played by Canadian Micheal Ironside), as well a nice waitress in the airport coffeshop which he goes every night after work and finally his prostitue girlfriend (an alway excellent, but criminally underused Jennifer Jason Leigh).
One cannot help but think that Edgar Allen Poe would be even happy to watch this movie in a morphine induced haze.
Two trivia bits: The movie was financed, shot and produced completely in Spain because nobody in hollywood would pick it up (the subject matter is dark but not as dark as I thought it would be). Look for a bizarre cameo from British Actress matron Anna Massey who is in the film for no discerable reason and given little to do.