#3 Heath Slater
Here's the thing about Heath Slater. He's funny. Like, really funny. Funny to the point where keeping him off TV week in and week out makes no sense whatsoever. SmackDown booked his union with Rhyno and pursuit of the tag team championship to perfection, but now that he's on Raw, he's hardly been heard from.
If they're not going to use him and Rhyno in a tag team capacity, WWE should at least put him in a managerial role. He can be paired with someone who could use a little dose of personality a la Apollo Crews with Titus O'Neil. The first guys that come to mind are Kalisto and Wesley Blake.
Yes, those two superstars are at very different places in their careers and the pairing with Slater doesn't immediately come across as logical. But neither did pairing Curtis Axel and Bo Dallas with The Miz or pairing James Ellsworth with Carmella. Anything can work if it's done well enough. Slater could make an overt attempt to bring the personality out of these guys and show them how well it worked for him. Just giving either one of Kalisto or Blake a mouthpiece could do wonders for them.