The one where you play across the whole internet
PMOGis a revolution in gaming. Taking the entire web as its framework, PMOG (passively multiplayer online game) turns your daily net-browsing activities into an RPG adventure, complete with traps, missions and treasure. You can sign up for the Beta phase and get involved right now, though the final version ought to be available soon enough.
With the Firefox PMOG add-on, you trawl the web as normal. Except that, occasionally, messages will appear identifying missions or quests for you to follow - trails of clues left by other players. Sometimes these lead to gifts or other benefits. Sometimes just to a nasty mines, stripping you of hard-earned experience points.
Along the way, you can chat or battle with PMOG users browsing the same sites as you, set your own missions (or traps, natch) and gather XP merely by visiting new pages. It's difficult to explain, and perhaps hard to get your head around at first. Once you're in, though, the internet will never be the same again.