#5 John Morrison/Impact
Yet another star that WWE dropped the ball on, some may say that Morrison's promo skills back in his WWE stint were not up to par, but that has changed over the years. After leaving, Mundo competed for various indy promotions, starred in several seasons of Lucha Underground, and recently appeared for GFW wrestling.
For a guy the weight of a lower heavyweight, Morrison can wrestle a style that makes it seem like gravity doesn't exist. During his time in WWE, he was never able to breach the mid-card ceiling and was relegated to the Intercontinental and Tag Team championships.
Not that the two respective belts are worth less, but Morrison was never given high profile singles matches to showcase his talent at it's peak. A definite dream match would be Morrison against AJ Styles.
His character and athleticism may be at it's prime now, but a move back to WWE does not seem optimal for Morrison. Even on NXT, the current overflow of independent talent would most likely result in him getting lost in the shuffle. For now, you can tune into his work on GFW Wrestling.