What is the most disturbing yet great movie you've ever seen? More specifically, what is the best Psychological Thriller you've ever seen? For me it's: A clockwork orange, Requiem for a dream, Kids, Memento, The Machinist, Session 9, and Bully

I would agree with A Clockwork Orange and Requiem for a Dream. Both very disturbing.

The Ring and The Grudge were both very disturbing - but very cool.
8MM was disturbing the first time I watched it too.
Saw and Saw IV were disturbing - from the gore point of view as well as the mental anguish inflicted on the victims. Interesting.

The Hills have Eyes...part 1

Possibly Eraserhead. It's awesome because the imagery is just damn creepy, but it seems to be symbolism used to tell the whole tale, I find this awesome.

Jacob's Ladder was also great, as was Trainspotting.

The Vanishing (Dutch: Spoorloos) is a French/Netherlands film adaptation of the novella The Golden Egg by Tim Krabbé, released October 27, 1988. Directed by George Sluizer, the film is about a young Dutch girl named Saskia Wagter (Johanna ter Steege) who disappears from a rest stop along a highway in rural France; her lover, Rex Hofmann (Gene Bervoets), cannot accept her disappearance and embarks on an obsessive search for her spanning years.
be warned nothing like the american version -this film will haunt or keep you contemplating it and its message for months-dont say you were not warned and dont blame me

jarhead...
serious shocking shit

First thing I thought of when I read your question was all of the historical movies I've seen (Braveheart, Roots, Schindler's List, Hotel Rwanda, etc. etc.) -- I guess it really disturbs me to be reminded of just how terrible mankind can be (and has been) to each other.
But as far as psychological thrillers go, the movie 187 with Samuel Jackson shook me up quite a bit (no spoilers in case you haven't seen it yet), I was bothered by the easy violence in Reservoir Dogs, Pulp Fiction, and Kalifornia. A Clockwork Orange disturbed me until the end, where he kind of got what he deserved; I haven't seen any of the others on your list but I plan to check them out!

I've seen and "enjoyed" all of your choices except I've not seen "Requiem."

Psychological thriller? 1997 " Funny Games " directed by Michael Haneke [ not the recent American remake, I haven't seen the remake ]


+5

The Butterfly Effect, with Ashton Kutcher.

I yet have to see requiem for a dream, memento, machinist, session 9, 11:14, november, donnie darko, prestige and many others. I loved almost all I watched. like: hide and seak, secret window, the beautifull mind, forgotten [maybe not much psycho], butterfly effect, identity, usual suspects[only the last part was a little like mind games. though wiki has it in psycho list] the night listener. and my brother's fav mulholand drive. maybe I'm forgetting some others. :)
woohoo a psycho thriller question :))))))

An Inconvenient truth...although Pulp Fiction's opening violence was so repulsive to me that I only watched the movie for a few minutes and never really saw it at all...

Clockwork Orange.

House of a Thousand Corpses and it's follow up, The Devil's Rejects, are both insane (Rob Zombie directed them), but they are really good.

Irreversible...it's a french film with Vincet Cassel and Monica Belluci...great great fim

Difficult one. A Clockwork Orange is definitely amongst them. I hated Requim, couldn't completely finish it even, though it really was a very good movie. Maybe I should watch it again, the timing wasn't right.
Wolf Creek is high on my list, very disturbing. If you ever see it, afterwards look for some information on Ivan Milat and the backpacker murders. It makes the movie even more haunting. Though the movie isn't about him, parts of it are based on the crimes he did.
I saw the Last House on the Left (Wes Craven) recently which is also high on the disturbance level. Not a comfortable movie to watch, to say the least.

It's difficult to answer, I have seen too many movies and can't remember half of them or I just forget to mention them :)

Das Experiment is also on the list, German movie based on the Stanford Prison Experiment. Though far from chilling compared to the others I mentioned, it still was a disturbing and a good movie. It shows you how normal people can get out of control pretty easy.
Funny Games (the original, also a German one) I saw last week. Great movie and yes, definitely a disturbing piece of work.
Henry, Portrait of a Serial Killer. Also good one. And oh, Man Bites Dog (C'est arrivé près de chez vous) is a brilliant one! Documentary style, with humor but also quite sick and chilling. A definite must-see! I saw that one in a cinema, and people actually walked away. (but they probably did with most of the movies I just described)
Hmmm..

I was just reading back my answer and realise that all of those movies have in common that they are having a high reality level. I think that is what makes these movies so chilling for me.

A disturbing yet great film, which is based on reality: Midnight Express.

And A Clockwork Orange is both one of my favourite films and novels.

In that vein I think "The Shining" and "Taxi Driver".