Everyone should have and know how to handle a firearm. If it's for home defense you can get frangable ammo for in the home. A 22magnum revolver would be sufficent. For fun you can't beat an ar or an ak. In actual truth it's actually second to full auto.
Preferably belt fed.
SKS is good, AK will function in mud, AR's are picky about a little sand. It doesn't matter. Just be able to shoot it well and know how to take it apart to clean it, and put it back together again.
The rest is pure choice. Only one will put a man down so he doesn;t get back up and that is the one you are using.