I went with Shotgun. I have a KelTec KSG and it would meet most all needs. It is very rugged, easy to conceal, holds a minimum of 15 rounds upto 25 rounds if you can find 1.5" shorties. 12G ammo should be easy to find. Multiple loads available from slug to shot. Good for hunting and accurate. Good for self defense. Zero tools needed to strip, clean or repair. Light since most of it is polymer also going for the durability.

I would of course also take a 9mm pistol or two but this only asked for the first gun.