I use a small 12V air compressor. They can be found at Wal-Mart type stores for very little money ($10-20). Cheap price, cheap product. I'm on my second one in about 4 years with occasional use. It's noisy and takes a long time to inflate a tire, but it is convienent. Also nice because I carry it in the trunk along with a plug kit, though I hope I never get two flats and have to use it.

On black friday the local Ace Hardware offered a really small pancake -style compressor with a hose, air chuck, etc. and even a brad nailer for well less than $100. No worrys about wanting to buy impact guns and such. Those little compressors won't push enough air to run them. I would have bought one but as an apartment dweller it would have been a production to string an extension cord out of the apartment to the car.