Most of the names I would have expected people to mention have already been mentioned, so I'll throw out a few lesser known or less obvious choices that I've always liked.
Dave Hope of Kansas, great P bass tone and some really tasteful and melodic playing.
Kyle Brock on some of Eric Johnson's CDs
Unless I missed it, Graham Maby wasn't mentioned yet either. Joe Jackson's material has changed a lot over the years but Graham's tone has too and has suited Joe's sound very well.
Mike Rutherford on old Genesis albums, great Rickenbacker sound!
Dave Hope of Kansas, great P bass tone and some really tasteful and melodic playing.
Kyle Brock on some of Eric Johnson's CDs
Unless I missed it, Graham Maby wasn't mentioned yet either. Joe Jackson's material has changed a lot over the years but Graham's tone has too and has suited Joe's sound very well.
Mike Rutherford on old Genesis albums, great Rickenbacker sound!