Boxing : Ancient boxing didn't have many rules, nor did it have rounds. Two fighters would keep going at it until the other was knocked out or admitted defeat. There were no weight classes (fighters were chosen randomly), and there was no rule about hitting your opponent when he was down.
The Equestrian Events: consisted of Chariot Racing and Racing. In Chariot Racing, there were carts pulled by 2 horses, and another pulled by 4. Each racer had to do 12 laps around the stadium track (about 9 miles). Horse racing had separate classes for full-grown and foals.
Pankration: Was a form of a combination of boxing and wrestling. The two entrants wore no hand wrapping. The only rules were that no biting, and the gouging of the opponents eyes were prohibited. Other attacks, like kicking in the stomach, were perfectly legal. Like boxing and wrestling, there were separate classes for boys and men.