Hep! 

After the players form a circle, one player must clap in the direction of the player to their right and say 'Hep!', this passes it to the person to their right, who must now do the same - this continues all the way around the circle. HOWEVER, if someone 'Heps!' you, you may also decide to say 'Oi!' which sends the Hep in the opposite direction around the circle. New rules are added continually, and chaos ensues.