I love gamifying my sadism, especially when I know I can't lose because I make the rules and can change them whenever I like.
In this clip taken from a real time session, I have my two slaves suspend a bucket from both of their balls by way of a chain with two clover clamps on either end.
Earlier in the day, I had them collecting stones and pebbles from the garden; now I am going to entertain myself by tossing them into the bucket and watching them squirm as it gets heavier and heavier, pulling down on their balls.