My third product in the cement- and "things-you-can-do-when-there-is-really-nothing-else-better-to-do" series: the Brick Game.
Main features: on and off (and two player bat controllers).
Backside: antenna and power connectors
When you put your ear on the brick, you can still hear cute Pong sounds from the far deep, cement is a good sound insulator.
Find a DIY guide on The Making of page