Stanley Proto J7099A 13 Piece 3/8" Drive Hand Impact Driver Set
I picked Proto's set as number one mostly based upon their quality. This is a company that manufactures tools for the professional; maybe not in the same league as Snap-on, but definitely as high as Armstrong and Mac. This is a 3/8 inch drive impact driver; which comes with two different sizes of hex adapters and 10 bits. As best I can tell, they're the only manufacturer that gives you two different sizes of hex adapters. Everything comes in a plastic case for ease of storage and to prevent loss. The impact has a heavy-duty spring for added torque.