http://www.harborfreight.com/12-in-18-volt-cordless-impact-wrench-60380.html
18v Cordless 1/2" Impact Wrench
After using my father's corded impact and finding it an embarrassing failure, I grabbed this with the intention of giving it to him. I figured I'd test it out beforehand, though, so I charged it up (2.5 hours to full). It seems well made. On looks alone, everything seems put together as well as anything else out there. It's not overly bulky or heavy. Looks like spare batteries can be had for about twelve bucks after coupon and tax; you can't beat that! After seeing that, I was kind of thinking about grabbing one for myself for when people need help away from an outlet to feed my portable compressor.
I got out an impact socket, a torque wrench, and a Ford Ranger for the testing.
Started off setting a lug to 200 ft/lbs, as that's the max on the torque wrench. No dice. Impact didn't budge it at all.
Took it down to 170 ft/lbs...nope. Nothing. 150 ft/lbs...it took some time, but it did eventually break the lug loose. Took it up to 155 ft/lbs...nothing again. Set the lug all the way down to the factory 100 ft/lbs...zipped it right off, no problem.
Well, there we go. Looks like the impact rated for 330 ft/lbs tops out somewhere between 150-155. If you just want it for removing lug nuts on your car or light truck, I guess it'll work out pretty good for you. If you want it to do what HF claims it can do, it's a fail. Beats the pants off of the corded unit by a hell of a margin, though.
Blech. I'm disappointed. I had gotten my hopes up. "Max torque" ratings are always a load of ****, even with Snappy or IR...but I was hoping/assuming I could at least get 200 out of this thing.