http://www.eve-online.com/

Quoting from the website:

''EVE: The Second Genesis, is a massively multiplayer, online, persistent world game. perhaps even too real to be called a game, but definitely more fun than reality. Played on the net by nerds who can't get a date, it takes place in a world that is alive and kicking every day, every hour. Players are spaceship captains cruising around the universe, trading, fighting and communicating with other players.''
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Uses StacklessPython for game logic on both server and client.