I haven’t read this entire thread, and I’m not sure if the OP is still taking requests, but…
Trench Mace ; WW1 trench-raiding weapon, craftable from wood and scrap metal/nails, or found in antique stores.
Muscovite ; A .22LR revolver made entirely out of scrap metal (high skills and gunsmithing tools required). Inspired by the made-from-scratch revolvers mass-produced by an unknown Moscow gang during the 1990s.
Manganese Matchlock ; Craftable one-shot pistol (pipe, wood, wire/string) using match-sulfur and manganese (matchbooks and vitamins in game terms) as the charge and scrap metal or nails as the shot. Low range, low accuracy, low damage. Requires a flame source to fire. Cannot be reloaded, only disassembled and remade.
Folsom Flamethrower ; One-shot blowpipe flamethrower made from nothing more than a rubber hose. Same range and function as the spraycan flamethrower. Requires a flame source to fire. Uses powdered non-dairy creamer as ammunition (which would need to be added to food-drops).
Chechen AK ; Full-auto AK modified to fire 7.62x54R. Craftable with high skills from any AK-pattern rifle and a SVD-pattern rifle. Generally uses a 20-round box (two SVD boxes welded together)
Windbüchse ; Large and bulky craftable air rifle, requires good tools and high skills. Fires ~.50cal bearings with range and damage comparable to a .45ACP. Very accurate, low recoil, relatively silent. Very fragile and easy to break if ever used for smashing or in melee.