'Clever' Movies. Movies you have to think about. Mind F*cks. Twist endings. What are the best ones?

If there's going to be one single movie meant to screw your mind, it's Videodrome. The director of it made "The Fly", "The Brood", "Scanners", amongst numerous confusing others, but the whole movie makes you believe it's all a dream.... And then it isn't.... And then it is again.... And then a guy gets shot and his body explodes because all of these tumors develop within him... Confusing. You'll need a cigarette afterwards because it WILL F*ck your mind.