Will Smith said no to playing Neo in
The Matrix, in favor of
Wild Wild West.
He later said he would've messed up the character because he wasn't mature enough to play Neo at the time.
Sandra Bullock said no to playing Trinity in
The Matrix because she couldn't see herself working with the actor considered for the lead role. Will Smith shade.
Christopher Lee's ass said no to playing Dr. Loomis in the original
Halloween because it was a low budget movie. Bitch.
He saw one of the cowriters at some kind of get together years later and said saying no to that role was one of the biggest mistakes of his life.
Bill Muarry didn't (or wasn't asked to) return for
Charlie's Angels: Full Throttle because of fights with Lucy Lui during the first film. Apparently, he said some really nasty **** to her. Bastard.
Patricia Arquette allegedly wasn't asked to reprise her role in
A Nightmare on Elm Street 4: The Dream Master because a behind the camera bitch didn't like that all of the guys from the cast and crew were swooning over her in
A Nightmare on Elm Street 3: Dream Warriors.
Arnold Schwarzennger was originally supposed to play Kyle Reese, Sarah Conner's baby's daddy, in
The Terminator. After Arnold and James Cameron had lunch together, that was changed immediately.
And in my mind, some would make pretty good renditions. 
