I've placed a bunch of small things to crush on the floor and make my slave sit down in front of the pile. I walk over his hands a few times - then reveal what I'm really planning to do! I move his hands between the stuff to crush and then put a blindfold on myself. Now I start to walk back and forth - crushing stuff and trampling the slave's hands under my boot soles. Of course this might hurt way more than usual since I don't see what I'm stepping on - and sometimes hit his fingers with only the edge of my heel or crush a piece of plastic into his hand :-D In the end I take off the blindfold and put it over the slave's eyes instead - and then continue the brutal finger trampling as he's really afraid and in pain!