I have this one
3/4" Air Impact Wrench cheap and good reviews, i dont have anything bad to say about it either as we use it for our semis from time to time too.
At this point im sure im not even using it to its max potentital, need to upgrade our air compressor.
For my other guns i have a dewalt cordless 18v 1/2 drive and a smaller 1/2 drive dewalt. These work super good as well, i have a few batteries for them and i use the bigger dewalt cordless for everything from wheel lugs, strut bolts, tierods, control arms etc. The smaller dewalt is good for tighter spots the big one doesnt fit or smaller bolts as to not tear them up.
The big air gun i rarely use on the car, mostly for things like the axle nut or ones the dewalt cant budge.
Small Dewalt-
http://www.amazon.com/gp/aw/d/B002VW...ogL&ref=plSrch
Big one-
http://www.amazon.com/gp/aw/d/B002VW...B0L&ref=plSrch
Had the cordless ones for a few years now and their use is almost every other day.