You'd probably only get laughs if you were to wave a tactical pen around when confronted by thugs, yelling "Back off! This is a TACTICAL pen!" But that's not what these things are about. The tactical pen is designed to be the sucker punch that any man, woman, or youngster can deliver when they get grabbed from behind, or otherwise taken by surprise.
If you have the pen within reach, you can grab it and drive it into the hand, wrist, groin, throat, eye or other vulnerable spot on an assailant. Most of these pens have a well-designed grip to keep the weapon where it belongs, in your hand; and any weapon in your hand is better than none at all.