Three-eights drive, cordless ratchet. I know pretty much nothing about these things, other than I see videos of other gearheads using them. I don't know which are good and which or meh, but Milwaukee Fuel appears to be the weapon of choice. I have zero experience using cordless hand tools; I've used pneumatic ratchets before and avoided them, especially when tightening fasteners - knuckle busters.
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Getting access to the fastener appears the be the main issue, once you're on it the tool does the rest. With manual ratchets, you need to consider handle "swing" (I'm looking at you, Toyota

).