We use a snapon one. Great for winding up M20 bolts by the dozen.
http://www.makitauk.com/products/front/?id=2202&model=BTW450RFE I got a few 18v lithium makita tools , batteries last the best compared to others ive worked with
and charge in no lenght , batterys arent cheap but if you have them there so many other makita 18 v lithium tools out there that take the same