Robin Williams as Jack Torrance - The Shining
Though he was only really known for his comedic television roles at the time, Stanley Kubrick foresaw the potential for Williams to get his dark side on and he was believe it or not one of the actors Kubrick first considered for the role of the maniacal Torrance (which would've given us a pretty damn twisted take on the Popeye/Olive Oyl romance). The book's writer, Stephen King, did not agree with the choice and the role was eventually offered to Nicholson. It wasn't until several years after Kubrick's death that Williams finally got to cross over to the dark side, with 2002's One Hour Photo. It's interesting to note that the iconic "Here's Johnny!" line was improvised by Nicholson, so we can be pretty sure that the line would've never been uttered had anyone but him taken on the role. Also considered by Kubrick? Robert DeNiro and Harrison Ford.
Jean-Claude Van Damme as the Predator - Predator
Van Damme wasn't just considered to be the guy to bring the Predator to life, but he was actually hired for the role, before the studio decided they needed someone more physically imposing in order to pose a realistic threat to beefed up stars Arnold Schwarzenegger, Jesse Ventura & Carl Weathers. There are differing reports that suggest that Van Damme just wasn't happy with the role, complaining about the heat of the heavy suit and the fact that he was essentially going to be an uncredited special effect, which offer alternate reasons for his being replaced by 7 foot 2 Harry and the Hendersons star Kevin Peter Hall. Either way, Van Damme was only on set for a couple days before getting ousted. The above photo is one of the only shots of Van Damme on the set, in the original Predator costume.
Dan Aykroyd & John Belushi as David & Jack - An American Werewolf In London
Having just directed Aykroyd & Belushi in the 1980 hit The Blues Brothers, John Landis was approached by Universal about re-teaming with the two for his next directorial effort, American Werewolf. Given that Landis wanted younger unknown actors to play the parts, he refused and went through a lot of trouble to bring non-movie stars David Naughton & Griffin Dunne on board instead.
Marlon Brando as Father Merrin - The Exorcist
Fresh off the heels of The Godfather, the studio wanted to bring some serious starpower to The Exorcist by casting Marlon Brando as Father Lankester Merrin. The reason the studio wanted him for the role was ironically the very same reason director William Friedkin turned down the suggestion; Brando was too big a star and Friedkin didn't want his demonic horror movie turning into a "Brando movie".
Leonardo DiCaprio as Patrick Bateman - American Psycho
Though many actors were considered for the role before Christian Bale took it on, including Johnny Depp (with Cronenberg at one point attached as director), Edward Norton & Brad Pitt, it was DiCaprio who was closest to swinging the axe, with Lionsgate even releasing a press release stating he would be doing so. Though he was offered an estimated 20 million dollars to play Bateman, in the film that was at the time to be directed by Oliver Stone, DiCaprio backed out and so too did Stone, leaving the film in the hands of Bale and director Mary Harron. Reportedly DiCaprio was talked out of accepting the part by Gloria Steinem, a well known activist who convinced him that the movie would turn off the majority of his audience. Oddly enough, Steinem shortly thereafter married the late David Bale ... Christian Bale's father. Innnnnteresting.
Gene Hackman as Hannibal Lecter, Silence of the Lambs
At one point in time, Hackman actually bought the rights to the book Silence of the Lambs, which he planned to turn into a movie. Furthermore, he intended on directing it as well as starring as Dr. Lecter. His hopes and dreams came crashing down when he watched a clip of himself from Mississippi Burning at the 61st Annual Academy Awards, wherein he realized he was uneasy about portraying violent characters. Hannibal ended up passing over Sean Connery too before he landed in Hopkins' lap.
Linda Blair as Carrie White - Carrie
Though Blair originally auditioned for the role of Carrie White, she eventually changed her mind and turned it down, over fears of being typecast. Ironically, Blair would forever be seen in the business as one thing and one thing only; Regan MacNeil. Carrie Fisher & Melanie Griffith also auditioned for the part of Carrie.
Sterling Hayden as Quint - Jaws
Spielberg's original vision saw Hayden in the role of Quint, but legal troubles prevented that from coming to fruition. Story goes that Hayden was in trouble with the IRS, with all of his money made from acting subject to seizure by them. A plan was concocted to pay Hayden, also a writer, very little for his role as an actor, and instead give him the majority of his pay by purchasing one of his written works for a large sum of money (the IRS couldn't touch the money he made outside of acting). For fears that the IRS would find out what they were up to, the plan was abandoned and Robert Shaw was offered the part. Lee Marvin was also offered the role, but told Spielberg he'd "rather go fishing".
Dolph Lundgren as Leatherface - The Texas Chainsaw Massacre (2003)
In what would have perhaps been the coolest thing ever, He-Man himself was approached to don the dead skin mask in the 2003 remake of The Texas Chainsaw Massacre, but turned it down to spend more time with his family. Interesting to note that the name of Lundgren's character in last year's Expendables was Gunner Jensen, an apparent reference to Gunnar Hansen, the actor who played Leatherface in the original Chainsaw. Strange ...
Christopher Lee as Dr. Loomis - Halloween (1978)
When a then unknown John Carpenter approached horror vet Christopher Lee to play Dr. Sam Loomis in his little independent film, Lee immediately declined the offer, as did Peter Cushing. After the mega success of the film, Lee admitted that it was the biggest mistake he ever made in his acting career.