Ultimate discs will work. Rules Two players in each court. You throw one so that it touches outside their court, they get a point. You make them touch both discs at the same time, you get two points. If you throw one in and one out, the score doesn't change.
Strategy Throw it into their court, instead of out.
You'd be amazed how effective this is even up through the highest levels of play. Try timing your throws so that both discs are heading into their court at the same time. When that happens to you, panic. They're not hard to make if you want to save some money. The courts should be 13-meter squares.