I carry a couple of things not yet mentioned. A small bell and some pepper spray.
As I often go geocaching in the San Francisco east bay hills by myself, I have taken to placing the small bell on my day pack so it dingles as I go along because I don't want to startle any large animals which may be nearby. Large animals like mountain lion, which ARE in the area but will usually get out of your way if they know you're there. The other large animals, like someone that has a meth lab set up in some remote area visited mostly by geocacher types. Hopefully, they will lay low, until you have passed if they hear you coming.
The pepper spray is for if they don't.
CCW permits in Kalifornia are almost impossible to get but, oh well, as they say, "It's better to be judged be twelve than carried by six"