Then there was the cassette that Newfsmith had which someone had tightened too tight. It took a bench vise, a lockring tool, a chainwhip, and a 24 inch piece of pipe to get it off. For a lockring tool, the kind with the center post are nice because sometimes your quick release skewer isn't long enough to hold the tool onto the wheel. Also note that putting the chainwhip on a larger cog gives you more leverage.