Holmes has to be the best of all time surely. So much power on it and relentlessly accurate. Frank Bruno also had an excellent jab and another very underestimnated one is Carl "The Truth" Williams
That's it for me with jabs, IMO to be considered good it has to have a bit of power. Not just used as a range finder or as some pitty-pat scoring shot.
For me recently DLH had one the best jabs, especially later on in his career. Wlads got a good jab. Khan's isn't bad however with Khan he NEEDS to have a good jab. Sweet Pea had a good jab, Barrera did and Foreman
My favourite jab currently is Wlad. I also like Juan Manuel Marquez's My favourite jab of all time is Buchanan. I also like Ricardo Lopez's.