JACO!!!!!!!!!!!!!!!
He invented that bridge pick-up tone,that has been copyed by thousands and thousands!Not to mention the Fretless
Then I go with Marcus of course for slaping(and he has been copyed a lot too).
Then every other great bass player has usually a beautifull tone,but not so personal as those two,from my point of view.Stanley also had his own sound of course,but I don't like it as Jacos' and Marcus' ones.
The list could start with Alain Caron for a modern sounding 6 fretless,and then with Patitucci when he played his Ken Smith in the late 80's.For the '70s funk,I go with the greatest Paul Jackson.
I personally find the Guy Pratt's sound with his growling Spector,great for Pop-Rock.