A "game" in which urban youths run up to unsuspecting victims and attempt to render them unconscious with a "knock out punch", usually from behind.
Also, a game in which urban youths get shot dead by law-abiding citizens who have a permit to carry a concealed weapon. The body count of these urban youths is expected to climb, as more and more of these dumbasses try to play this "game".
(as heard on a news report): Today, another young black teenager, aka thug, died of wounds he received after being shot trying to play the "knock-out game". He attempted to punch an elderly lady from behind, because he's a chicken-shit, but to his surprise, after she fell to the ground, she drew her gun and shot this piece of shit right in his fucking face. The woman claimed she will sue his mom and dad (if his mom even knows who the daddy is) for pain and suffering, as well as reimbursement for the rounds she used. God bless her!"