The spare/jack/lug wrench is a given from me on at least a travel trailer.
OK, outside of that, in reverse order is
3. Spare fuses. I mean spares for everything from what's in the electrical distribution box, to any inline fuses.
2. A multi-meter
1b. Spare set of keys. I managed to lock my keys up in the RV, so it can be done. I've also left home without them, and couldn't open the doors.
Of course with a coach, it's not likely you can leave home without keys.
1a. Air inflator/gauge