http://smile.amazon.com/gp/product/B002MUAUJM/

It has saved my bacon several times. At least 3 times during the time that I've had it, I've gone out to my car in the morning only to find that I have a flat. Each time, I was able to pump up the tire, throw this in the trunk, go to work, then pump up the tire again before heading to get the flat fixed. I love the portability of the battery, and it has the option to use the cigarette lighter as well if you don't have enough juice. It's also easy to quickly top off my tires when needed, and again, I don't have to fight a cord when doing so.

It also has another setting for more volume and lower PSI for blowing up air mattresses and stuff too.