Cavemen still living without the magic of air power (and I’m one of them) will find a neat workaround in the form of hammer-actuated impact drivers. They’re old-school, clever little devices which turn the force of a hammer blow into torque, and plenty of it. Hit the casing with a metal-faced hammer, and a cam inside gives you a strong twist, exactly like a pneumatic impact wrench.
Though not quite as user-friendly or useful as an impact gun, they can still get stubborn bolts in or out. $25 is pretty cheap considering that it’s a Craftsman set. Even if you can find a pneumatic impact gun at that price, no one in their right mind would trust it, and these let you skip the compressor, too.
Impact Driver Set [Craftsman]