Pioneer Courthouse Square of course. And to update, I'm going to have cards with paper clips that you can slide onto your con badge or clip to your pocket with 5 small red tabs.
When a player targets another player, they say "I challenge you!" and both players hold their left hand out in a fist touching the opposite player's fist in a Battle Bond. There is no refusal, and no one else can challenge either player until one round is done. A round has passed when both players have attacked once, regardless of hit or miss. When the round has passed, both players drop their hands and count off 5 seconds. If someone comes up to one of them and says "I challenge you!" before they finish counting, then the one challenged plays a round with the new player. If no one challenges within the 5 second count, both fighters may play another round, or withdraw from battle by saying "run!" When a player is hit, they pull off and pocket a number of tabs for each point of damage. When they run out of tabs, they're out for the game. Play goes until there is one left standing, as the Champion. Then everyone receives new cards and plays another round. The Champion gets a card with gold tabs and scores an extra point of damage in battle. Each player's card will also have a special power on the back that they can use to attack instead of a normal Rock-Paper-Scissors attack.
And I'm doing the Battle Bond instead of a handshake so that no one squeezes someone's hand too hard.