Magic: The Gathering/Assassin Format
Assassin Format is typically played in groups of five or more. The name of each player is put into a hat (or whatever) and each player draws a name, to be kept secret. The rules are thus: A player may only attack the player whose name they drew, or any player that has attacked them at any point in the game (universal effect cards can be played, just as long as your target could be hit with it, e.g. Skullcage, Radiance). If they drew their own name they may attack any or all other players (strategy here, simply build up your forces until you can swamp a player, since no one can target you until you attack them). All types of spells, with the exception of those with universal effects, may only target the player drawn or players who have since attacked you (counter spells, creatures, instants, sorceries...). Any method of attack goes. Speed rules are usually enforced, since this format tends to take over an hour to play.