TetrUs is a co-operative tetris game that uses peer to peer connections between clients. It uses jp33r for managing its network connections, and is the reason the library was first created. There are plans to implement multiple game modes, including single player, full co-op (currently implemented), split co-op and possibly even an MMO tetris mode.
You can download the TetrUs beta for free and play with your friends. The current version has scoring, and levels up to 11.