Besides the volt/ohm meter and other stuff everybody has mentioned, I also carry battery powered tools. Before Home Depot did away with cashiers (I won't take someones job away from them and refuse to work for free at Home Depot checking myself out) I got a selection of their Ryobi battery powered tools. I carry a couple of chargers (of course) a battery powered drill, reciprocating saw and air compressor. The air compressor has proved to be invaluable. When I went to Missouri, two other RV's had low tires, one nearly off the rim and I loaned it to three neighbors who had foot pumps for their air beds.