Modify the rules so scoring in your own goal doesn't count?
Ultimate frisbee captains can, I believe, agree on any subset of rules before a game begins. The inclusion and use of dodgeballs on the field was one modification of note.
Another figured out that swimming upside-down under water was faster than back-stroking above the water. Alas, this innovation was banned. And so it goes.
Politics gets into it, as anyone who followed the UCI's wars with Graeme Obree would remember: