Some may argue that this isn't a horror movie. They're wrong.

The Wiki:
Seconds is a 1966 American film starring Rock Hudson. Characterized sometimes as a science fiction thriller, but with elements of horror, neo-noir, psychedelia, and drama, it was directed by John Frankenheimer with a screenplay by Lewis John Carlino. The script was based on a novel by David Ely. The film was released by Paramount Pictures and was entered into the 1966 Cannes Film Festival.
Arthur Hamilton (John Randolph) is a middle-aged man whose life has lost purpose. He has achieved success in his career, but finds it unfulfilling. His love for his wife of many years has dwindled. His only child is married and he seldom sees her. Through a friend, a man he thought was dead, Hamilton is approached by a secret organization, known simply as the "Company." The Company's business is helping wealthy people who are unhappy with their lives to disappear and create new lives. When Hamilton agrees to talk to the Company, he is spirited away to a secret location. While waiting for his interview he is offered a cup of tea and then falls asleep. When he wakes, Hamilton is interviewed by Mr. Ruby (Jeff Corey), who shows him a film in which he appears to have raped a girl. The film, made while he was unconscious, is intended to persuade Hamilton that it is now too late for him to return to his old life. Hamilton feels compelled to accept the Company's services -- but fears that this coercive scheme foreshadows the unfortunate consequences of doing business with the Company. Hamilton's death is staged to make it look as if he perished in a hotel fire; a corpse is left at the scene that can be identified as his. Through extensive plastic surgery and mental and physical conditioning, Hamilton is transformed into Tony Wilson (Rock Hudson), a man who looks and acts much younger. He is provided with a new home, a new identity, new friends and a devoted manservant. The details of his new existence, including diplomas and other evidence of professional accomplishment that appear genuine, suggest that there was once a real Tony Wilson, but what became of him is a mystery. (I'll leave it here as to not spoil the rest of the film)
Beach Boys co-founder Brian Wilson saw the movie during its initial release, between sessions for Smile. Under the influence of drugs, the early stages of schizophrenia, and pressure to complete Smile, Wilson found Seconds an especially intense experience, that affected him personally (beginning with his arriving late; the first dialogue he heard onscreen was "Come in, Mr. Wilson", taking him by surprise). His state of mind shifted over the next months, between fantasies of escaping his own life in a similar way, and thoughts that perhaps rival producer Phil Spector had somehow convinced Columbia Pictures (sic) to make the movie "to mess with my mind". Wilson later abandoned the Smile sessions, and did not see another movie in a theater until E.T. the Extra-Terrestrial in 1982.
Thoughts:
This is a trippy, freaky, amazing film from John Frankenheimer, one of my all time favorite directors. The cinematography by James Wong Howe is hypnotic and eerie. Seek this one out, it's so worth it.
WATCH THE TRAILER here:
http://www.youtube.com/watch?v=DQhlCRpuX8Y