From 1954 until his death by illness in 1995, Dr. MarionTinsley was the World champion at checkers.  During this 41-year period, he only lost seven times.  He is considered by everyone to be the greatest checker player who ever lived: veritable HumanPerfectionInCheckers.

The man-machine world champion in checkers is now the computer program Chinook.  You can read the fascinating account of Chinook's development and battle for supremacy with Tinsley in JonathanSchaeffer's book OneJumpAhead.

To his credit, Dr. Tinsley welcomed the opportunity to play against Chinook on more than one occasion, even though there was the possibility that it might defeat him.  Many other players, and the top checkers association (anyone remember its name??) refused to play or to sanction such man-machine matches.  In the context Dr. Tinsley could have easily escaped playing the machine and remained world champion until his death [it turns out that he did anyway].

More info about Tinsley for the curious can be found at:

http://www.chess-poster.com/english/chesmayne/marion_tinsley.htm
http://www.acfcheckers.com/mft.html

And in many other places (Google).