How useful is a HANDGUN for protecting your family if SHTF?

Everyone here seriously thinks that "the shit is about to hit the fan". How many of you have a weapon to protect yourself and your family? I'm thinking about getting a handgun for an "apocalyptic" scenario. I'm trying to protect my family from an alien invasion, foreign army invasion, thugs, looters, and wild animals (maybe even zombies).

I'm just curious as to how many of the GLP members have actual weapons that will somewhat protect them in such scenario. I have no weapon at all, maybe a few knives, and I'm trying to purchase a handgun. If the government doesn't "approve" for me to have one then I think under the US Constitution I can just buy one or make my own.

We really don't know what can happen, we can have an alien invasion, we can have Russians or Chinese soldiers invading, or an asteroid could hit the Earth killing almost everything and the survivals will have to defend themselves with something.

Hopefully I can get one before "the shit hits the fan".