My 2 bits. For doing all those things you mentioned except the 12 volt application you could get a really small compressor. Smaller than a pancake. Craftsmen made a decent one, don't know if they still do. Senco has one, about 140 or 150$. I know the Home Despot has a couple of small compressors geared towards homeowners. I've got an oil free pancake compressor, works fine for me unless i'm sheeting something or framing walls. Then it has a hard time keeping up. For the vehicle, they sell pressure tanks that don't have a compressor motor for refilling tires. Might look into one of those.

http://www.amazon.com/Senco-PC1010-Horse...711&sr=1-17

that's the senco at amazon.

Just remember these compressors all have a duty cycle, easiest way to ruin a compressor is to run it past it's duty cycle. If you are using a compressor to spray air everywhere don't keep that thing running for several minutes on end, it will start to get hot.