Before I get started, I have to quickly talk about the biggest ego in baseball history...George Steinbrenner. (I kept this list to players only.)
He proclaimed in order to make money you have to spend money. He wasn't the cheapest owner. The Boss always signed all of the top free agents.
In a 20-year period, he hired and fired 20 managers, including Billy Martin five times.
He was truly the first owner who dictated an entire organization.
As for the "egos" on this list, the term doesn't necessarily have to have a bad connotation to it. Some players thrived off their egos, some were clubhouse cancers, while some had quiet and confident demeanors.