4. Dr. Jekyll and Mr. Hyde
The 1886 novel written by Robert Louis Stevenson, inspired many television and film adaptations, and created a common genre trope of a man with two conflicting personalities. The story has inspired such films as The Nutty Professor and its box-office hit remake of the 1990s with Eddie Murphy.
While the story has become somewhat cliche, a direct adaptation or screenplay inspired by the original story could offer screenwriters a great platform and character base to work from.