For survival, I'd take a nice reliable12 ga. pump action shotgun (like a Mossberg M590) and even a 2nd gen. Glock 17 as long as there's sufficient 9mm ammo and 12ga buckshot shells.

For SHTF situations and dealing with an advancing zombie horde, I'd take something like this:



The AA12 Atchisson Assault Shotgun with a 32-shell drum magazine.