I think any pen being pointed, can be tactical. If I got stabbed in the neck, I dont think it would matter if it was a 50 cent bic pen, or a $100 fancy one.
I'm of the opinion if you are left stabbing somebody with a pen, running would probably be a better option. There are some pretty cool ones though, like the Boker bolt action pen.
My Fisher Bullet will stab and break anything a tactical pen will, but it doesn't look dangerous, so no one will need to confiscate it, nor will I end up on charges of carrying a concealed weapon which could easily happen with many of these tactical pens.
Tactical pens make middle aged men think they are still cool in the office. So when the young new girl needs a pen he can whip out his uber cool Ti supa dupa pen and impress her. It's a foot in the door (he thinks) to then bore her stupied with the technical details of the pen "it can write upside down you know, or write in space, cool eh?". They also give a great false sense of security as the owners think they will be able to fend of crooks or wild animals with the said pen. Apart form the above, they are hard wearing and you can write with them.
While not many of us are dangerous assassins with amnesia, that is an excellent example of using what is around you rather than trying to carry a pile of stuff you may never need.DefSent from a digital multitool