I love the psychological effect of a parachute harness or a scrotal cuff. Especially with a leash attached. It's not the actual sensation so much but rather the idea of what a sharp, hard jerk on the leash would do.

It certainly causes you to follow with alacrity when the Domme walks away at a brisk pace. I've always been amazed at how fast I can move on my hands and knees with the right motivation. eek