I got the honor of watching the ridiculously secretive black belt class the other day. My instructor was teaching pressure points, but because of my presence he was not going into depth. Because I was actually doing computer work, I didn't get to see much, but this is what I did see.
My instructor was demonstrating what he said was an easy pressure point to hit, without needing too much technical know how, just the ability to sidestep/angle/whatever, and a good fast front kick. He told the student to do whatever he wanted to try and stop him. The student threw a right hook. My instructor (almost blindingly fast) parried and grabbed on to the student's arm with his right hand, angled to his left, lowered his body to pull the student down popped him on the underside of his arm, on the side of the elbow closest to his body. The student immediately dropped down and said that he couldn't feel his arm. After seeing that the student was ok, he said that particular pressure point was used in the application of a technique at the beginning of Heian Nidan. I'm guessing it's the "c-block" technique. He then saw I was paying too much attention and asked me to hurry up. What pressure point was this he was hitting? It appears to be very effective.