Glenn is the voice of reason here. I can't believe how hard people make this... it's simple:
DON'T OPEN THE DOOR TO SOMEBODY YOU DON'T KNOW... NOT FOR ANY REASON, EVER! JUST DON'T DO IT! It doesn't matter whether it's day or night, if you have a dog, if the kids are home, if you have a gun, if you have a security system, if a cop lives next door, if you're a cop, if you're a black-belt, if there's a trap-door under the welcome mat, NOT FOR ANY REASON EVER!!! F&%K!!!
About 99.9% of your door-knocking problems can be solved by the simple application of a "NO SOLICITING" sign on the doorbell. It doesn't have to be fancy... in fact, the more plain it is, the more impact is conveys.
A doorbell camera/intercom system is the icing on the cake. You don't even have to get up from the couch to see who is knocking... and you can retreat to the bedroom or wherever your primary defensive position is and call police.
Of course everybody should have at least a basic CCTV system covering the entire exterior of the house, and a simple home-alarm system (even if not monitored), that can be activated in the event somebody at the front door doesn't get the hint.
Our family practices a standard "trouble" scenario, which everybody to runs to the master bedroom, the wife to immediately dial police and stand-by on the alarm panel while arming herself, the kids inside the closet, and dad at the bedroom door in a concealed position to cover the main hall and exterior bedroom window. There are variations on the scenario, but they never start with dad being a moron and opening the front door to somebody he doesn't know. And my kids know they are NEVER allowed to open the door unless I tell them too, even if it's somebody they think they know.
My primary defensive weapon is a 12ga pump backed up with a G17, both equipped with a light and laser.
If you don't have one of these, ask yourself why not? My setup is different, but the wireless funtion of this one gives you another tactical advantage of being able to talk to the person at the door while on the move inside the house:
http://www.amazon.com/Entry-Guardian...pd_sim_sbs_e_4
