Well I would include Dodgeball as most people did not believe it was true, or many of those semi-fictional Japanese sports (binocular football!)
However, the winner should be brokian ultra cricket from the Hitchhiker's guide to the galaxy:
"a team sport that involves people beating each other with sporting equipment, then apologising from a safe distance. Like real cricket, the rules of the game are massively convoluted, leading to a perpetual state of war between the players over their interpretation."