I think purchased a 12v cig plug type airpump with light at my local walmart for I think around 20 bucks or so. Nice to have around. Esp when you get a flat tire driving home at night like I did two months ago.
A cool thing about the pump is that it has an auto-stop feature. Basically you set it at what PSI you want and it'll stop pumping air when it reaches that point.
I got my first ever tire puncture yesterday.
A nail caused slow leak so I put on the spare tire.
I had fully inflated the spare tire to the recommended 60 psi about 5 months ago but yesterday it was down to 5 psi. Since I always carry a small 12V pump it only took a few minutes to inflate.
Moral of the story: Carrying a small 12V pump in the trunk is more useful then an air compressor tank in the garage.