It's an ARMA II: Combined Operations mod that turns ARMA into a persistent zombie survival game. Your character is the same on every server, down to where you were last. Staying alive seems to be pretty difficult, but there's an interesting video series where a guy survives for several hours. Here's the first bit
Just to give you an idea of how good this mod is, it put ARMA II: Combined Operations in the top 5 selling games on steam in like a month, I think.




