Well, nothing really. Like, I think that’s all the stuff you can find when digging through rock.
That said, I remember a fairly successful run where I had my survivor just tunnel through a city. I’d find a house with a basement, then I’ll dig through the map where houses are and see if there are more basements to be found. Found a lot of gun basements that way without the hassle of going through zombie infested streets.
However, I did that on the old item spawn rate, plus jackhammering now takes a little more time plus you can get hit multiple times by a zombie when you dig through a basement wall.