Head Ball, or, more specifically, Head Ball 2, is a mobile sports "game" that Joe is quite the fan of, having spent hundreds of dollars on over the years for in-game items.
Lars, Ohan and Richard frequently poke fun at Joe on-air for playing this game, citing it as being quite casual. Joe himself is on record stating that the game is "stupid", but notes that it is enjoyable despite the silly premise.
One of the ad reads for Mint Mobile included a reference to Joe being concerned about his ability to continue playing Head Ball in the future if he switched networks.
On EP70, Joe initially claimed to have quit playing the game, only later to contradict himself in admitting it was the only thing he had played recently.