Playing pong might not be anything new, but how about multiplayer pong? With the PONG! Multiplayer extension for Firefox you too can challenge your friends and foes in a battle of pong combat.
This extension also features a full blown chat application. Chat with everyone in the Multiplayer lobby, or just with your opponent while playing a game. Want to take on your best buddy? Just type the nickname or ip-address of a friend, and he/she will get invited to play a game against you.