In honor of the late, great Dr. B.M. Smith, aka Brewmeister Smith from the martial arts classic Strange Brew, here is a new technique to put in your GURPS games. It's as effective as the double-handed Shatner punch. Which is to say, it's awesome.
Head Crusher (Hard)
Defaults: ST-4 or Wrestling-4.
Prerequisites: Wrestling and ST 15+; cannot exceed prerequisite+3
You can crush your opponent's head like a nut. To use this technique, you must first grapple your opponent by the skull with two hands; see Grappling (p. B370). Your victim may attempt to break free on his turn. If he fails, on your next turn,you can squeeze. Roll against your Head Crusher skill. Success inflicts Thrust crushing damage. Grappling adds +1 per die if you know it at DX+1, +2 per die if DX+2 or higher. Rigid DR (including the skull) protects normally. Such damage is incredibly painful - double shock penalties (up to -8, or -16 with Low Pain Threshold). Head crushing can also be used as an influence roll - substitute a roll against Head Crusher for Intimidation, or add damage inflicted to your Intimidation roll, whichever is better!
This technique is frightfully effective on henchmen and on armored lunatic hockey players.
I lowballed the ST requirement; Brewmeister Smith is extremely strong, capable of holding up a grown man by one ear with a pinch grip with casual ST. But even ST 15 weaklings should be able to learn this technique. Below the requirement, you can try it, but not study it.