Hector Camacho
Meldrick Taylor
Naseem Hamed
Ray Leonard
Thomas Hearns
Roy Jones
Shane Mosley
Floyd and Manny

Some I think of right away, kind of hard to rate. I'd guess it would always be guys at the lightest weights for pure speed, and combination punchers tend to flatter themselves in a way. Guys like Hearns, Nas, Floyd at 130, Roy etc had devestating speed in single shots, Camacho coudn't hurt anyone but was like a cat with his combinations. Larry Holmes had really fast hands for a HW, as did Tyson.