Everyone always laughs at hitting someone in the head with a punch/can of beans/baseball bat/2x4/karate chop/whatever and knock them out. The joke being that the person will wake in ten minutes or an hour like in the movies and they'll go about living again.
In real life if you knock someone out cold with some kind of hit to their head ... you've more than likely killed them or put them in a place where they will die within the next hour or two.