The SX-210 from Mitsubishi pen of Japan is an inexpensive pen for your everyday writing tasks that can double as a makeshift kubotan. Not in wrist-lock techniques, but in the stabbing mode. The reason is its solid one-piece construction.
The refills srew in from behind (!) and the butt end there forms a nasty point. Pointed enough to hurt an attacker a lot, yet safe enough not to pierce skin (no guarantees, just my impression) . The cap just snaps on and off, but is very secure with an unusually positive “click” (the same on my second sample, so this is the norm on this model). The writing experience is EXACTLY “somewhere between a ballpoint, a rollerball and a gel pen”. Hard to describe, but very smooth and the ink dries extremely fast (lefties take note!). I have noticed no tendency of skipping, if you apply at least a decent amount of pressure to the pen. It also works perfectly on carbon copies. And if you have a tendency to write fast, these were invented for you.
If your favorite office supply dealer does not stock them, you can get them cheaply from the fleabay straight from Asia, the refills also. Even if you find that they cannot replace your favorite Kubotan (they are not meant to), you will like them as plain pens. Check them out, i love mine!