I voted for everythig up to NBC...
The unrestricted ownership of weaponry has to be viewed in the Libertarian context where it is possible, and conversely, the Libertarian context it would help create.
You'd have to imagine a Libertarian state, a-la L. Neil Smith where this is possible. Perhaps a "Libertarian States of America" or the parallel world of the North American Confederacy of his Probability Broach novels...
The LSA or the NAC would have no taxes, therefore no powerful central government to threaten the freedom of it's citizens.
Much of all "crime" is done away with out of sheer irrelevancy, because only acts that are Malum Per Se, (i.e. acts that directly harm others) are offenses. This means no drug wars, no gangs, no mob, no addict crimes, since they all exist and fight over the profiting from artificial scarcity created by governmental fiat.
Everyone who wishes to work, even part-time, can earn a living wage, as the lack of government regulation and taxes, and the lack subsequent burdens passed along through consumer goods etc. effectively doubles, triples, and quadruples the buying power of the individual.
External terrorists do not attack the NAC because it's a giant Switzerland, neither friend nor enemy to anyone. It just "is", and any dealings with other nations are between its individuals and consensually formed groups, and not the "state". There is terrorism, but it's domestic, and caused by those looking for their own self-serving pretext to establish an authoritarian regime.
Therefore while these weapons are possible, few bother to own them since they're still expensive, inconvenient to operate alone, and not really needed. Those that do have them, fear the direct retribution of their neighbors from misuse than some long drawn out process of courts and charges from the state. Fiscal liability is also swift and certain, there is no "bankruptcy" protection from the state. If Joe Sixpack blows up your house with an "oopsie" with his 81mm mortar, the courts will likely award you his.
Most military vehicles and crew served weaponry is really owned jointly (like partners in a yacht or plane) by local militias that serve in lieu of standing armies.
NBC is still frowned upon as it violates the non-initiation of force. It is nearly impossible to employ them without harming innocents.
Aside that, Balog and others make the point that we marshal destructive forces comparable to artillery and RPG's every day. They're called cars.
Who would you feel safer next to? A gun-nut neighbor who owns an RPG in his safe, and takes it to Knob Creek for some fun, or on the freeway one lane over from soccer-mommie in a Hummer H2 doing 65Mph while simultaneously talking on her cell phone, applying makeup, and scolding her kids in the back seat?
It's all kinetic energy and foot-pounds. The difference is merely in our heads. It's a matter of semantics and perception, one is a "weapon" the other is a "car". In reality, both are "tools", and you want to be standing in front of neither of them.
And as others have pointed out, privateers, merchants, and trading forts all possessed privately owned cannon in colonial times.
It is also worth noting that when you look at things like Waco, is a government monopoly over "military weaponry" really somehow "superior"? Ask a Native American or perhaps a Jew.
All of the great disasters, genocides, massacres, etc. have
all been caused by government, or at least the abuse of government, and not by a "lack of government". Even the current genocides being conducted in pseudo-anarchistic regions of Africa were really facilitated by one side being gullible enough to disarm at government's behest.