I once watched a bike mechanic break two freewheel tools, one after the other, while he laughed, obviously not realizing that he was the problem, not the tools. I took over, grabbed our last remaining compatible freewheel tool from the display case out front, and tightened a quick-release skewer onto the tool -- with enough force that the other guy protested that there was no way the freewheel was going to budge.

Placed the tool and wheel onto the shop vise, turned the wheel just enough to break the freewheel free, loosened the QR skewer a bit, and turned the wheel a little farther. By that point, the freewheel was loose enough to back it all the way off by hand.