I use a Dewalt DW059B. It's good for up to 300ft-lbs. Amazon sells the bare tool for a good price (see
http://www.amazon.com/DEWALT-Bare-To...+impact+wrench), and batteries aren't too expensive either.
I use it all the time on my 911, which has the bolts torqued to 118lb-ft. The Dewalt has no problem breaking the bolts.