Sandbox action game Just Cause 2 was a blast to play solo, but sadly shipped without any kind of multiplayer. No matter. Fans of the game's PC edition have whipped up a version that lets 600 people play it at once. On the same island.
The results are predictably...insane. Note that this is a fan-made thing, and is still in testing, so probably has a wys to go yet before it's "done". Still. Even what's on show here looks great.
You can check in on the mod at the links below.
Just Cause 2 Multiplayer Impressions 1 [YouTube, thanks Doug!]
Just Cause 2 Multiplayer [Site]