shell game
1. A game in which an object is placed under one of three cups or shells, which are then moved around. The person playing the game must guess the final location of the object. Don't play any of those stupid shell games at the carnival, they're impossible to win!
2. By extension, a method of deception that involves hiding or obscuring the truth. Primarily heard in US. The appliance salesman played a shell game and switched the refrigerator I agreed to purchase with a used model. A Ponzi scheme is a type of shell game that always fails because it relies on money from new investors in order to pay old investors.