Fighters that come to mind:
1. Meldrick Taylor: only fighter I've seen who I think had faster hands than Roy. While his hands were faster, he had slower legs, and reflexes than Roy, couldn't punch as hard (p4p), and wasn't as intelligent or disciplined. He had great combos though.
2. Pernell Whitaker: great defense overshadowed his superb hand speed and beautiful combinations.
3. Hector Camacho: Like Whitaker, but less consistent and slightly less talented/mentally tough.
4. Manny Paquaiou: elite speed, able to use awkward rhythm and fast hands/feet to overwhelm opponents with scary power and creative angles.
5. Vasily Lomachenko: A more complete/scary version of Manny. In my opinion, best combo of speed and power combos since Roy, with better fundamentals.
6. Mike Tyson: blazing speed combined with one punch knockout power in both hands. Great combination puncher in his prime.
7. Marvelous Marvin Hagler: scary demeanor and one punch power over shadows his boxing ability, speed, and combination punching. Hagler was a pro and in his prime he threw some beautiful combos with scary power mixed in.
8. Sugar Ray Leonard: great boxer who used amazing hand speed to overwhelm legitimate, ATG fighters like Tommy Hearns.
9. Floyd Mayweather Junior: One of the greatest ever. Used hand speed and combinations to dismantle Chico, Gatti, Hatton, and many others.
10. Roberto Duran: like Hagler, his savagery and punch overshadowed his speed and combination punching. Duran was one of the best at creating openings with the first couple of punches in the combination so he could land the last 3 or 4 of the combo. He also was one of the best at closing after hurting an opponent.
11. Roy Jones: when talking scary speed and power, no one captured/exhibited those traits more than Roy, he pretty much defined vicious, fast combinations. Watch his combos vs. Percy Harris, Brannon, Montell Griffin, James Toney, Paz, Reggie Johnson, Merqui Sosa, and Thomas Tate to see truly vicious, and fast combos. Scary stuff...