。。。Go for the body parts that can't grow flesh no matter how fat one can grow. Collar bones, solar plexus, elbow and knee joints and caps, shins. Real fights end in seconds, not like in movies, boxing or wrestling bouts.
Of course, the weakest and most vulnerable body part is the groin. However, police (or even gangsters of honour) would respect that's no go area unless in last resort of self defence.