#1. CM Punk
CM Punk walked away from WWE back in 2014, but he was able to make his return when he signed a contract with FOX and began working on WWE Backstage. The current job allows Punk to talk about WWE's programming and interact with WWE stars without actually working for WWE.
Whilst rumors have suggested that the former World Champion was looking to make his return to the company and a match with Seth Rollins at WrestleMania was brewing, this actually wasn't the case and Dave Meltzer of The Wrestling Observer later revealed that Vince McMahon reportedly doesn't ever want to work with the self-proclaimed 'Best in the World' again.
McMahon labeled Punk as the “one man I just can’t do business with" which makes sense since Punk went on to say some defamatory things about McMahon following his departure and was then taken to court by WWE's doctor Chris Amann.
Whilst Vince McMahon isn't open to a WWE return for Punk, it appears that both Stephanie and Triple H would be prepared to welcome the former Champion back in the future.