Self defense techniques.
So lets say that you're going about your own business and some idiot wants to bring trouble your way and be abusive and violent. Well you can always turn the other cheek or face them head on.
There are several weak spots on the body that can be exploited for combat advantage. The best way to knock someone out is to hit them in the side of the jaw to shake the brain causing loss of consciousness. http://i.ytimg.com/vi/UF-gA26ZHxk/hqdefault.jpg
Another weak spot on the body are the knee caps. The knee caps cover patella bones which are the largest sesamoid bones in the body surrounded by cartilage. A good strike should immobilize them.
And since we have opposable thumbs don't be afraid to fight dirty. Throw heavy objects. Go for the eyes to gouge them, or if you're feeling up to it grab them so they can't move and bite them. On the face, the neck, or eyes pick a part.
One of the hardest parts on the body is the forearm. When karate students break boards they use the forearm. Next time use a forearm strike instead of a punch. Or a head butt. A crescent kick can do as much damage as a punch.
And of course there's the groin. And it's not very hard to injure, just like the toes which can be injured easily by stubbing them, or a well placed shot to the solar plexus.
With these weak spot and strong spots in mind next time you will have options when some scumbag gets in your face.