You have a lot of negotiating power when you have the pen in your hand and are ready to sign the contract / buyers order!
The number one in my mind (as it's a safety issue) is a mounted spare tire!!
Some things that folks get thrown into the deal are:
Replacing the crappy rear TV with something like a Samsung smart TV that you can actually watch at ANY angle.
An extended warranty.
Some think that fog lights are a nice add-on.
Many feel that the tank-less water heaters are not ready for prime time, and get them changed out for a normal water heater. And of course, why be forced to use your own propane for hot water, when you're already paying for the electric at the campground.
And, last but not least, a couple of 12v electric fans.
However it turns out, be safe and have fun camping!!