While having sex in the doggy style position, grab hold of the girls pony tail tightly and as you are about to climax shout out the name of her best friend. You have to try and stay mounted to her as she twists, turns and bucks like crazy to try and get you off her.
There is usually no way back in a relationship if you are foolish enough to try this with a serious girlfriend. Make sure you have no intention of maintaining a friendship with this woman afterwards.
Some guys have actually found themselves in court on charges including battery and rape after some of the recipients of a "Bronco" have felt humiliated and abused and sought revenge. In court a woman has the right to say "No/stop" no matter how far along in the sexual act they are, so just a word of warning if you think this sounds hilarious!