ive tried 3 cordless rattle guns (hitachi, bosch, Makita all JUNK) my current one ive had for 4 years and use it everyday. Its a 18v snap on item and is the best one around, its damn expensive but is spot on. It comes with 2 batterys and i only have to swap it once or twice a week
i have a few air guns (GP, bluepoint and snap on and again the snap on / bluepoint one is hard to beat)