DC-9 and MD-80 could readily back with reversers - some operators did use that as SOP back in the 1980s (I was on an MD-80 more than once that used the reversers to back out of the gate). In addition to not needed the tug, since the aircraft was under control of the captain they didn't need as many ground crew spotters so there was a significant labor savings. However it did present a FOD risk and is pretty abusive on the engine in general - I think the operators quickly realized the increased engine maintenance cancelled out the labor savings.
Most commercial jets can back up with their reversers provided the ground is reasonably level - I was on a test on a 767 ~25 years ago where we demonstrated backing with the reversers. But it's so abusive to the engines and is such a FOD risk that no one does it unless it's an emergency.
The YC-14 could readily back using the reversers (and with the engines above the wing there was minimal FOD risk), - I suspect the C-17 can as well.