Shane Mosley in his prime welterweight days had awesome handspeed. The fastest hands of all-time? Roy Jones.
There is probably a whole slew of fighters who had speed to burn, but due to other shortcummings never managed to break through to Mainstream awareness, i do remember one Guy, Kenneth Gould is name was, Welterweight prospect of mid eighties as i recall, Had very fast hands indeed when he let them go, i think he had eye trouble and drifted away, but in some of his fights there was the hint of a young leonard about him I am sure that there are many other "Speed Merchants" who didnt break Through Mike Dokes when Young and Emerging was also Very Fast Handed as in His Ist Fight with Weaver.
They weot as powerful nor thrown with as much behind them most of the time, but he definitely moved them quicker.
PBF at 130. Judah is damn fast at welter and Camacho was fast at 130. Meldrick Taylor deserves an honorable mention.
RJJ seemed so fast because he had a better brain than most other fighters so he could anticipate punches meaning his reflexes seemed better.
Roy Jones had faster hands than Leonard and Meldrick Taylor had faster hands than Roy Jones. All are three of the fastest p4p though.
It was not just reflexes, though. As i've said before: no one in history has been succesful with throwing leaping left hooks and landing them time and time again, even when their opponents knew they were coming. That's pure hand- and footspeed.
agree with above posters on RJJ, in that those fast punches were hurtful KP blows rather than flurries and this should count IMO. Mention for Meldrick Taylor as well; lightning.