shell game

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A game, usually involving gambling, in which a person hides a small object underneath one of three nutshells, thimbles, or cups, then shuffles them about on a flat surface while spectators try to guess the final location of the object. Also called thimblerig.
2. n. A fraud or deception perpetrated by shifting conspicuous things to hide something else.

Wiktionary

1. n. A game of skill which requires the bettor to guess under which of three small cups (or shells) a pea-sized object has been placed after the party operating the game rapidly rearranges them, providing opportunity for sleight-of-hand trickery.
2. n. Any confidence scheme, especially one involving the rapid movement of investment funds to a location beyond recovery.

WordNet 3.0

1. n. a swindling sleight-of-hand game; victim guesses which of three things a pellet is under