I'm an old bastard (and bassist) who grew up on early '70s rock, so my three favourite bassists are McCartney (c'mon, you can't deny it...), Gene Simmons (he may be an asshole, but he sure knew how to rock that thing back in the day), and Dennis Dunaway, from the original Alice Cooper band. It's not that any of them are virtuoso players, but they know what's required, and their basslines are interesting and TASTEFUL, dammit!
I agree with conatonc, too.....from the more recent crop, Karl Alvarez deserves major props. Damn, that boy knows melody!
And Andrew Weiss, the Bassosaurus.