Probably the most successful of the list, Brock Lesnar was truly a sight to behold.
From the beginning he was placed in feuds with the Hardys, Hulk Hogan, and The Rock for cryin' out loud! He went on to defeat The Rock at Summerslam to become the youngest WWE Champion in history (at age 25).
Then he went on to have a feud with The Undertaker in which he defeated him in a Hell In A Cell match.
Then in a title defense against the Big Show, Paul Heyman turned on him and thus his face turn ensued. He went on the win the 2003 Royal Rumble match.
He then began a great feud with Kurt Angle, which culminated at Wrestlemania 19 when he regained the WWE title.
After that feud, he went on to have his last one with Goldberg which culminated in the entire pro wrestling world turning on the both of them when news spread of both of their pending departures from the WWE.
He then went on to become a Hall of Fame NFL player (just kidding). He is now currently the UFC Heavyweight Champion.