Milwaukee 2763-22, M18 Fuel 1/2" High Torque Impact Wrench
Milwaukee has several excellent cordless impact wrenches to choose from. I've picked this one as their best, mostly for the power it offers. Like the Matco below, it has 700 ft. lbs. of constant torque (in mode 2), and 1,100 ft. lbs. for busting nuts loose. The tool is variable speed with an electric brake. That adds a little bit of safety to using the tool. It also has a LED light to light up the work area; this is a nice feature finding its way onto more and more power tools. The anvil on this tool uses a friction ring to keep the sockets in place and while some people prefer a detent, I find a friction ring easier to work with. You can buy the tool as a bare tool or in a kit with two 4.0 Ah, 18 volt batteries, and a multi-voltage charger.