I use a Milwaukee m12 3/8" fuel impact for most bolt work including working on the suspensions of my 66 mustangs. The thing has been a boss and i love it.
I have a Milwaukee M18 1/2" for bigger things. It's had no problem spinning nuts off my tractors. It is a heavy brute though so I have to eat a can of spinach or some Wheaties.
I used to have CP air tools fed by a 24cfm air compressor but have started moving everything over to the Milwaukee battery tools. They seem to have more torque, portable, take up less room, no hose to get in the way, and are just more friendly for me.