Something to think of in the unspeakable scenario — where will you get ammo? Wal-Mart ain’t open anymore. Your ammo will likely come from a) whatever you have hoarded over the years and b) what you can beg, borrow, or steal from whatever military / LE presence is on the ground.
This tilted me towards the 9mm pistol and .223 rifle. I’ll likely always be able to scrounge some .223, much harder to scrounge up 7.62x39.
At any rate, I believe everyone needs at least four guns: a .22 rifle for hunting small game, a good, reliable, reasonably accurate pistol, a 12 gauge pump shotgun, and a military-style rifle. My choices are a Ruger 10/22, a Glock 17, a Remington 870, and a AR variant. Your mileage will mostly likely vary.
consider this.
my pistol of choice is .38super. yep, ammo is hard to come by, but i have a good sized horde of it, and a ton of cases and powder. but consider this, if SHTF and for some reason i have to drop it, is becomes 90% useless to whomever picks it up. OTOH, .38super fires the same projectile as 9mm, so worst cases scenario, i have a gun that mostly useless to other people, but with a few minutes work pulling bullets from 9mm, i can have ammo.
teh same goes for a couple of my other guns. components are common, but factory bullets aren’t. also, i’m hoping to start casting my own soon, which will make it even better for me in SHTF world.
Exactly the point I was going to make! Right now, ammo is available most places, but in a real SHTF scenario, the supplies will be locked up tighter than tupperware. Once you run thru your cache you have two choices: roll over and die or live off the enemy. That's why I have stuck with NATO standard weapons and ammo. Of course I included many of the former NATO standard for our military from when I was active (45ACP). I have at least 1000 rds per caliber that I own of high quality go to war combat ammo. This is distinct from the shooting supplies that I keep on hand and continually use for practice. I even stocked up on a couple thousand rounds of the old 45 Winchester Back Talon on the theory that nothing is too good for the enemies of freedom. My biggest worry is that if things go too off the chain in a post election meltdown of anger, that some tepid soul will holler for UN Peace Keepers to be invited in to restore order and democracy.
If that happens we're toast. We'll never be rid of them before they mangle the nation to the degree that it becomes unrecognizable as the USA as we know it now.