When you look at the tactical pen M-TAC TP-17 , you can see it right away that the design was inspired by Kubotan.

Kubotan is a non-lethal active defense tool that looks like a keychain. It was invented by Kubota Takayuki , a grand master of martial arts from Japan. The concept is simple – it's used to deliver pinpoint strikes to the attacker's vulnerable spots. The same approach is followed with the tactical pen. The only difference is that you do not carry it along with your keys, but rather in your pocket and you can also write with it. 14.5 cm long handle made of aircraft grade aluminum with anodized finish. Ribbed surface for tighter grip. On one side there is a glass breaker ( which is also the striking part ). On the other side there is an ink holder, covered with a cap with a clip.