#9 Rusev
Rusev is another Superstar who is greatly talented but who hasn't been booked nearly as he should be.
He's won a US Title here or there, but it appears that he just isn't someone creative values high enough anymore to consistently book him as a title holder or contender.
The latest example of that is how he is now being booked in a tag team with Shinsuke Nakamura. Didn't Nakamura just mock his wife's injury and wasn't Rusev just in another slightly successful team (albeit with no titles) in Rusev Day?
The Bulgarian Brute has even recently stated that he's frustrated that no matter what he says or does to catch Mr. McMahon's eye, it doesn't change things.
That type of frustration and in a public matter is a big sign of wanting out of the current situation. He's been displeased before so this might be close to the last straw.
Rusev may be a WWE creation, but his talent isn't strictly something created by WWE. In backstage segments and interviews, he shows enough personality that would get him over anywhere.
Although he's still under contract for a while, he might have to continue to eat crow until it expires. That or go the Neville route.
Whatever he decides to do, it wouldn't be much of a surprise if he left WWE once his contract expires.