Piñatas are containers in Diablo III. They can only be found in Whimsyshire, Whimsydale and the Whimseyshire tileset in Rifts.
They are destructible, and when destroyed will drop loot similar to that found in a Resplendent Chest.
They are the only way to obtain the Horadric Hamburger, chance to get one increasing with difficulty.
The container itself appears as a stereotypical childplay Piñata (the papier-mache container kids break with a stick to get candies), but is shaped in form of happy smiling mini-Diablo.