Tough to narrow it down, there have been so many great jabbers. Guys like Hagler, Hearns, Spinks, and Whitaker aren't listed, and they had great jabs too.
Also, i'd just like to throw this out there... Comeback Foreman had a better, harder ramrod jab than Sonny Liston.
I have not seen any footage of Robinson in his prime which was at welterweight so of the ones listed I say Holmes had the best jab. Hearns is also up there and I also think that fat ******* Tony Tubbs had great jab. Not the best ever but he certainly outjabbed more than one opponent so he gets an honorable mention.
I think the best one is Holmes' in terms of effectiveness, but I voted for Ike's as I like the position from where it is thrown and motion more [ame]http://www.youtube.com/watch?v=q6lwjwWaiik[/ame]
I would say Holmes, because he used his jab to control other fighters. Holmes jab is the tools he used to win fights, if he was left with just his jab he could still win.
say what u will bout the guy but from a technical standpoint, i'd say felix sturm throws beauitful jabs.