Do you want the toughest compact wrench on the block? The 18V Hitachi WR18DBDL2 may just be the one, with its unique IP56 rating and powerful 305 Nm brushless motor.
It’s not cheap, but do you really want a cheap impact wrench?
Impact Wrench http://amzn.to/2tvPOSG
https://www.hitachipowertools.com.au/en/cordless/18v-slide-brushless/wh18dbdl2-hx-detail