A MUST HAVE FOR ANY RV IS A SURGE PROTECTOR. Progressive Industries is our top choice for protecting our RV, from high and low currents that some campgrounds can have. Our 50 amp surge protector has found, in a few campgrounds bad wiring, and allowed us to move to different sites before we even unhooked from the truck. We have the portable EMS-PT50C RV Power Protection with Surge Protector and the first thing we do is plug the unit into the electric outlet, wait until it shows good current for both L1 and L2 poles and then plug in the power cord if all is good. This is the one we have and has a lifetime guarantee
http://www.progressiveindustries.net/#!ems-pt50c/c1ma0
Another thing that we have are X-chocks, to keep the tires from moving before, during and after setup.
At least one extra sewer hose, in case needed for extra length to sewer drain.
Extra water hose, for same reason as sewer hose. (Some campgrounds put water and sewer connection to far back).
A portable ceramic heater, incase the weather gets cold and you don't want to use propane. Easy to heat bedroom using campgrounds electric verses heating all of the unit on propane. Just turn on furnace in the AM or keep on low until morning.
We also have a kurig coffee maker, and portable ice maker. We have the standard RV fridge and it takes up to much space making ice cubes, so we make it in ice maker the transfer to ziplock bags.
We also for same reason above have a small 3.5 cf chest freezer for the extra meats and frozen good like ice cream.
As far as composting toilets go, no thanks. Our old RV dealership had one, and no matter how many times they changed the composting material, it always smelled like a barn. They changed it back to a regular water system 6 months later.
Just a couple things we carry just in case unexpectedly needed.