Les Claypool (Primus, etc.) - 50 - Unique, percussive playing style, over multiple instruments from 4-string basses to 6-string fretless, to upright. Can sing and play these rhythms at the same time, just boggles my mind. Capable of improvisation and deep jams with other musicians. Some of his basslines literally get stuck in my head for days, like Duchess and the Proverbial Mind Spread. Probably my favorite musician, so I am biased.
Justin Chancellor (Tool) - 10 - writes some amazing rhythms. Paired with Danny Carey, one hell of a foundation.
Phil Lesh (Grateful Dead) - 15 - innovator on the bass. Playing lead instead of strictly rhythm, and all that improvisation that made the Dead who they are.
Mike Gordon (Phish) - 15 - proficient in so many styles. An exceptional improvisational player. Phish will take you on a goddamn musical journey.
Roger Waters (Pink Floyd) - 10 - not the most technically proficient bass player, but much of his songwriting is still relevant today. Plus, there is some great bass playing on Animals, Meddle, DSOTM, WYWH, and The Wall. I'll never tire of the groove in Echoes. Granted some of these lines may have been written by Gilmour.