#2 "Stone Cold" Steve Austin

Steve Austin was the biggest star in WWE during the infamous Attitude Era, even bigger than wrestler turned actor The Rock. The latter became a much bigger mainstream star, but Austin was the face of the company at the time.
That's why it left many fans shocked when Vince McMahon publicly announced that Austin "took his ball and went home" on the 3 June 2002 edition of RAW. The internet wasn't as vast as it is today, so many people had little knowledge that this was going to happen or why it happened.
Apparently, WWE Chairman Vince McMahon wanted The Rattlesnake, his biggest star, to put over Brock Lesnar, who was still a rookie, on a normal episode of RAW with no build-up. Austin refused to do the deeds, arguing that the match should take place in a bigger stage with proper build-up.
That sounds like a reasonable explanation, but the higher-ups didn't agree to it, so Austin walked out of the company. He returned to WWE the following year and wrestled his final match against The Rock at WrestleMania XIX.