Bare minimum though you really should have two of each of the following with two complete replacement parts sets.
Handguns
Colt Peacemaker - 45 long colt
1911 - 45 ACP
Browning HiPower - 9mm
Ruger or similar .22 semiauto
That is all you need as far as handguns
Long Guns
Kentucky Long Rifle or Brown Bess
Winchester 1886 in 45-70
Benelli semiauto shotgun 12 guage
M16 -full auto or burst .223
AK47 full auto
M1 Garand 30-06
M14 - .308
SAW - .223
Browning .30 cal. belt fed
Ma Duece - need one say more
Barrett 82A1 - see above for ammo
BAR - 30-06
The above is of course a bare bones minimum and one should really have at least two of each type, though three or four would be necessary to make one really comfortable with such a cut down list of weapons.
Each individual weapon should have at least 100,000 rounds and the belt fed probably 10 times that number.
Of course the conveinence of such a bare bones inventory is that you can pack it up in a jiffy and take it with you if you need to. Also in a pinch you could carry half of it concealed.
This doesn't touch on artillery, mines, RPGs, gernades, ect.....fortunately there is an even simpler shortcut when trying to establish a bare bones inventory of area weapons - you can easily get by without most of the above by merely substituting 4 to 5 hundred claymores and just 4 or 5 one megaton yield nukes.
The firearms you can pickup just about anywhere with a few simple forms and a little cash - check the couch cushions. The nukes are either a do it yourself project - did you take high school physics? Or I have heard recently that there are people just dying to import a few nukes into this country.
Glad I could help.