This is NOT legal advice. If you mess around with National Firearms Act weapons and do something that you should not do, you will very likely go to prison. Seek competent legal advice.
Any Other Weapons
Any Other Weapon is the BATF designation for anything that does not fit Machine Gun, SBR/SBS, Destructive Device, Suppressor, or regular firearms. They use it as a catch all and add things to it.
I mentioned the wallet holster for the Beretta .25 autos. At one time, they sold these in any gun shop. It was leather, had an open top for the slide to function, a finger hole for the trigger, and screwed to the grip frame. At some point in the 90s IIRC, they decided that since it attached to the gun and disguised it, it was NFA regulated and a person needed to go through all the red tape and pay the $5 transfer tax. AOWs also include a pistol with a foregrip - added to the definition sometime in the last few years. Say you have one of those AR15 pistols and you put a rail on the fore end. If you add optics or lights to the rail, no problem. Add a foregrip to it and you are a felon without going through the AOW process. Some historical guns such as the H&R Handi Gun are also AOW. That was a pistol gripped .22/.410 over/under with a 10" barrel made in the teens and 20s that folks carried on nature hikes or in their Model Ts. Disguised guns such as cane guns, pen guns and flashlight guns are AOWs.
I discussed suppressors (BATF calls them silencers) a couple weeks ago when I reviewed the Silencerco Sparrow for my Ruger .22/45 pistol. You'd think that they would be AOW with a $5 tax, but they are considered firearms by BATF and need the $200 tax. Prior to 1934, you could literally walk into your neighborhood hardware store and pick one up for $5 or $6. In much of Europe, the use of a suppressor is favored or even required at public shooting ranges, and they can still be bought over the counter. People from the city move out to the country and then complain about the noise of gun fire. Any long time shooter probably has some hearing loss because people didn't use to be as cautious about hearing protection as they are now. Imagine how much nicer it would be for shooters and their neighbors if suppressors were still easily available.
Come back tomorrow for Destructive Devices and suggestions for NFA weapons for SHTF situations.