George Lucas
How many people are aware George Lucas was the 'unofficial' Executive Producer?
It was repayment of a favour to Lawrence Kasdan, who came aboard and helped George with the script for The Empire Strikes Back when it was sorely needed (after Leigh Brackett's death), and would script Raiders Of The Lost Ark for him.
He did what Francis Ford Coppola once did for him, and helped shepard Kasdan's directorial debut. But left his name off the credits, because he thought audiences would get confused about his name on a neo noir, and would think of Star Wars.
"Everyone else may be an a**hole, but I'm not!" - Harlan Ellison