I use a Dewalt 12v cordless 3/8 square drive impact at work everyday. It is the best way to get the small/medium fasteners on and off. The biggest factor in performance is the battery. After years of use the batteries get weak and performance drops off dramatically. Check around online to see if batteries are still available, and maybe pick one up.
For the tighter spaces you can pick up a cordless ratchet if needed. Just note that they are pricey!
GC
