I came out of my local Costco the other day and this was parked next to my diesel pickup. The first thing I spotted was the Moon tank on the roof rack.

 Overall, it was a nicely done up pre-'97 XJ. I didn't get the exact year. He had a 4- or 5-inch lift, some 31s, nice bumpers, and a roof rack with multiple ammo can storage and this 5 (ish)-gallon Moon fuel tank with what looked like an air valve on it.

The rig had Arizona plates on it. I'm not sure if he filled it with a volume of compressed air, water, or gasoline, but the quick-release male chuck on the tank bottom looked like air. I wasn't aware these tanks sealed effectively enough to be used as an air tank. Guess I won't know for sure. Either way, it's cool use of a neat hot rod component on an off-road 4x4.