I don't think of "favorite musicians" in a vacuum. I judge them not so much on "them," but on how I like the music they played a role in making.
Those would be the ones who played on the widest range of stuff that I like – which is primarily '30s–'70s American music that was marketed primarily (or entirely) to a black American audience – or "R&B," for short. I can narrow that down farther, to the classic periods of Chess, Stax, and Motown. From there, I'd have to name their most commonly recorded studio bassists, which would be Willie Dixon, Duck Dunn, and James Jamerson. I hold all this music in pretty equal regard in terms of quality, though each has a different and distinctive type of R&B sound. If I really had to pick one of those three over the others, I'd pick Stax.
Therefore, my answer is Duck Dunn.
Is he the best bassist who ever lived? Nope. But he played the bass on the greatest music ever created (if I was truly pressed to pick). That is far more important to me than "how good" he, or anyone else, was/is.
Not so surprisingly, then, Steve Cropper is my favorite guitarist, Al Jackson, Jr. is my favorite drummer, and Booker T. Jones is my favorite keyboardist.