For the non-athletes, Charlie Finley, Bill Veeck and Chris von der Ahe.
All three have been considered for the Hall of Fame (Veeck is in). Finley and Veeck were well known for their outrageous experiments.
von der Ahe was probably less controversial, but he was a publicly bombastic personality. He was "der boss president" of the St. Louis Browns. He had a
statue of himself erected outside Sportsman's Park. A lot of his interest in having a baseball team was as a mechanism to sell food and beer to the fans. Cap Anson suggested a championship series where winner took 100% of the gate receipts - von der Ahe accepted to everyone's surprise and then St. Louis won.
He's probably not as controversial as others, but he's a great part of 1800s baseball history, so I like to mention him when I can.