1) Hunter Zolomon (The Flash)
Hunter Zolomon was recently introduced in The Flash as the Earth-1 doppelgänger of Jay Garrick, so utilizing him as the big bad of season three gives the series a way of keeping actor Teddy Sears around and means that Barry Allen will be able to square off with a very different type of speedster next year.
Hunter became Zoom after Wally West – who was serving as The Flash at the time – refused to risk damaging the timeline by travelling back to save him from being paralyzed in an attack by Gorilla Grodd. Taking matters into his own hands, the criminal profiler gained the ability to alter the speed at which he could move in time, giving him the effect of superspeed, but making him very different from Zoom and Reverse-Flash. It then became his mission to kill The Fastest Man Alive, which would make for a great personal conflict on the show.