Flea, John Entwistle, Verdine White, Roger Glover, Donald "Duck" Dunn all come to mind as great bassists. Michael Anthony too. Flea redefined the role of the instrument IMHO, he's way more important to the sound of the RHCP than the guitarist.
Finally we have a winner!
Leland Sclar is very entertaining however, I follow his short Youtube videos, even made a brief cameo appearance in one

when he walked the line outside the Birchmere last year. At 7:44, behind the guy with the cowboy hat on. This was for the Lyle Lovett tour.