I have a Cold Steel Shark (which can be seen on the same link posted above). It's about like a thick Sharpie marker. Some of the "tactical pens" are ridiculously priced for what they are. Basically they're employed similarly to a yawara stick. But you can't sign your name with a yawara. I carry a Surefire flashlight much more frequently because it can be used employing yawara techniques, plus a flashlight is useful in more situations-- to see where your going, to locate something, to blind an attacker.