Probably all been named but here goes, in order of 'this guy invented things and can do things others can not':
Jimmie Blanton: This is the single person responsible for the way bass has been played in all modern western music genres. Let's call him Issac Newton of bass.
Stanley Clark: This guys is the Albert Einstein of bass guitar. Theroies may be refined, but it will be a long time before someone provides the Grand Unified Theory of bass, and until that time, Clarke's E=MC^2 will be the definition of what can be done on this instrument.
Jaco Pastorius: If Clarke is Einstein, this is Niels Bhor.
Les Claypool: Sticking with the physicist analogy, here is Richard Feynman. Les has acheived a level of technical mastery of the instrument which rivals that of jazz players, blending funk, rock, jazz, slap, and other 'sound-effectsie' elements together in some of the most complex and inventive playing around. A true wizard! The father of strange world of QED is a fitting analogy for the father of the strange world of the Primus bass player.
Paul D'Amor: I see some of you listed Justin. Justin Chancellor was asked to copy D'Amor's style, and play his already written parts on Aenima, the rest is an extension of writing and playing bass parts in same vein. Paul's suffocating swampy drop D and drop E style and syncopation with Adam Jones IS the defining sound of Tool. To credit that sound to Justin is criminal. Just is technically excellent, but he didn't invent anything. He is essentially a session guy. I'm putting D'Amor above the next guys simply because I like his sound more than any other in rock.
Bootsy Collins: The master of funk, and arguably the father of much of the bass sound you hear in post-modern rock. The list of people who list Bootsy as their greatest influence is immense, bring me to the next guy...
Paul McCartney: Perhaps not the fastest, slickest, or flashiest, but do not underestimate any member of the Beatles. This is another person of very high influence on all rock music.
John Cale: This might be another head scratcher for those of you who disagree with Paul McCartney. Basically most of the rock music you hear today owes everything to a handful of bands, and none more so than The Velvet Underground.
Noel Redding: Another high influence guy from a high influence band, The Experience.
Cliff Burton: The defacto inventor of speed metal bass. A lot of people would plae Cliff higher on this list, and I can understand that; he was a master and one of the first in rock to approach the instrument as if it were a guitar, but his influence is mainly limited to a genre of music I find utterly boring, ultra repetitive, grating, and shallow.
Apologies to:
VICTOR WOOTEN
Roger Waters
John Paul Jones (he always get's fucked)
Mike Gordon (he can play anything, any style, anywhere, anytime, and probably do it better than the inventor, and find a way to do it on a garden hose)
Rob Wasserman
Chris Pravdica
Robert Trujillo (not for his Metallica shit)