The Zap Orb is an orb from Mario Party 6 and Mario Party 7 that will subtract coins from opponents. Just place it and any player who passes will lose as many coins (3 or 5) before the player's turn ends.
In Mario Party 6, if Yoshi has twenty coins and advanced fifteen spaces, then he will lose 75 coins (five coins per space) for a total of 120 - (15 x 5), or 120 - 75 = 45 coins. In the next installment of Mario Party 7, it is three coins per space. So Yoshi will have 120 - (15 x 3), or 120 - 45 = 75 coins instead of 45.