I recommend the Russian Saiga rifles and shotguns. It is basically a proven AK-47 system except the trigger assembly is moved more to the rear of the receiver to accommodate a sport wooden stock so the weapon becomes an import sporting rifle. The wooden stock can be removed and replaced with a handgrip and assault rifle style stock. Other parts can be replaced so it meets BATF requirements (i.e foregrip, magazine, etc) for enough compliant parts to make it still a legal semi auto import. The nice thing about Saiga’s is it comes in 5.56mm, 7.62 x 39 and .308 cal as well as a .410 and 12 GA mag fed shotgun. You can have a stash of these rifles and you need to show someone once on how to operate, load and unload weapon. Same procedures can be used on the various caliber rifles and shotguns. Lot cheaper, AK reliable and more rugged then an AR-15 system.
For a really poor man arsenal, revolvers (.357 mag that can also use .38 cal) and Marlin lever action rifles that uses the same bullets. No mags to deal with, just get tons of bullets for the standoff. Smith and Wesson and Taurus have some real nice 8 shot revolvers. These are very easy weapons to use and teach someone to load, unload and fire. Also add to the arsenal a .22 cal rifle and revolver for hunting and training. Ammo is plenty and alot cheaper then blowing off larger caliber bullets. You save them for the real thing.
I gotta second post #11. (Did post in my sleep under a different handle? LOL) That said, I own only one Saiga, the semi-auto 12, and it rocks.
As to the rifle, I do own an AR. No complaints for what it is but I wish I’d gotten a beafier caliber than the 5.56. 7.62x39, .308, whatever and then ability to switch to cheaper-shooting upper if desired. .22 uppers? No problem. You can even get an upper to shoot the PS90 rounds - talk about your low profiles!
If you pick an AR, skip the front-sight gas block & carry handle. A decent holosight is fine. Check previous banglist threads for recommends. Within the past month there WAS one about that very thing, I think. If you insist, you can add BUIS and a carry handle to your rails.