I’ve discovered that a pinch of meth really gives you wings when you’re getting your ass kicked. I always keep a hit or two on me should I find any.
Also, I’ve found a Rivtech short shotgun fits in an ankle holster, making it a perfect “oh shit” gun: it has the power of a big gun yet fits in a holster, so I don’t drop it to make room in my inventory and then end up not having it when I need it. I often carry about eighteen rounds of extra slugs, which stays under the threshold of a single point of volume. It’s even better than molotovs against some of the more powerful individual playthrough-enders like jabberwocks. I imagine a 12-gauge pistol would probably make an OK substitute if you’re not lucky enough to stumble upon a Rivtech short shotgun and ammo. I don’t know if a sawn-off is small enough to fit in a holster, though.