#2 Matt Hardy
WWE doesn't seem too interested in pushing Matt Hardy as anything other than his brother Jeff's tag-team partner. This was the case while both of them were in WWE previously as well.
Jeff Hardy was seen as a big star while Matt was never put on that level.
What we have learned about Matt in the last few years, however, is that he's very creative. The #Broken universe he created in TNA is arguably the most over a Hardy storyline has ever been.
That the WWE isn't using his creative mind at the moment seems like a waste.
Before he re-signed with the WWE, he was having main event matches with the Young Bucks in ROH and could likely tour the country selling out smaller venues doing the same if he was to leave.