I can't believe nobody has mentioned porta-potty.....

After porta potty I would have to say the Vitrifrigo fridge and solar panels
has got to be the best upgrade I've made.   Nothing beats being able to hand
out ice pops to kids 3 days into camping.  I also like not having to throw
out unused food that was sitting in my original fridge after campout because
I knew it had been up to 55-60 degrees.  And I don’t miss waterlogged food
from a cooler.

Bryan