Mental Floss has an article about what your favorite movie was almost called.
Here are a couple examples:
Blazing Saddles
Script writer Andrew Bergman originally called his 1974 Western spoof (and the lead character) Tex X, as a sly nod to Muslim leader Malcolm X. But director Mel Brooks was never enamored with that title. One morning when Brooks was taking a shower, the words “blazing saddles” popped into his head. Considering the classic bean scene, the new title seemed apropos.
Tootsie
Would I Lie to You? went through at least a half-dozen re-writes by as many writers before it finally hit the big screen in 1982 as Tootsie. The new title was suggested by star Dustin Hoffman (it was the name of his mother’s dog).
Back To The Future
During the filming of Back to the Future, Universal Studios honcho Sid Sheinberg fired off a memo to all involved in the production stating that no movie with the word “future” in the title had ever succeeded at the box office. He suggested that the name of this project be changed to Spaceman from Pluto. According to writer/producer Bob Gale, Steven Spielberg “earned his executive producer credit” by stepping in and sending back a note that thanked the studio head for his “joke memo.”