Y'know, the whole "tactical pen" thing seems kinda hokey to me, unless you're going to train hard to learn the kubotan or yawara stick. These are basically aikido (or related) moves and techniques, and here's a typical video. I don't see much in that video that's likely to work except for the beginning showing some vital points and general jabbing-striking moves. Any metal pen would be fine for that. Every tool you have at your disposal helps, so I'm not saying the "tac-pen" is worthless for SD, but to be a really effective weapon the user is going to need to train for quite a while to master the various joint locks and shin na style grappling that the kubotan magnifies.