As far as golfers are concerned, I think Sam Sneed was probably the best athelete - however you want to define it. About three years ago, I was able to play Sam's home course (You should go do it if you have the opportunity, great course - there is actually three of them). One of our caddies was an older gentleman who used to caddy for Sam and Jackie (Sam's son). Now Sam's flexibility is legendary, but apparently he also had tremendous strength. Moreover, our caddy said that it was well known that Sam could have played professional baseball, but less well known that he could have probably played professional football as well.
An additional item of interest regarding Sam - John Anselmo (one of Tiger's coaches when he was a teen I believe) used Sam as the swing model for Tiger.
While I don't disagree with Brian's assertion that JD has the best pivot of all time, Sam cannot be far behind. Also, the late Mike Austin used Sam's swing as a model swing.
dennis