When was the last time you played an online game (and no, Farmville does not count). This list above reveals the most lucrative free-to-play online games in 2013. Right on top is a South Korean first person shooter called CrossFire, which took in nearly $1 billion in revenue last year.

CrossFire was first released by SmileGate in South Korea back in 2007. The game is somewhat similar to Counter-Strike with its dozens of maps, game modes, weapons, and characters. Check out the gameplay below:

[Daily Dot]