In my case I need a small footprint 12VDC air compressor to be used for airing up or topping off my truck and trailer tires as well as providing a positive air source to blow out my trailer water lines for winterizing at a moment notice since we do alot of camping off the power grid.
I use the Q Industries portable MV50 12VDC 150 PSI Air Compressor available from AMAZON. It fits in its nice carry bag under my truck back seat. I usually sit this on my truck tailgate and hook into the trailer batteries and then I can use the provided long air coil hose to walk around the trailer and tires...
I also use this air compressor along with the CAMCO 36153 Blow Out Adapter to blow out my water lines for winterizing. Being TANKLESS it takes more time to build up air which is ideal for blowing out water lines.