One of my favorite female sadists writes about perverting an egg topper:
It’s essentially a stainless circle with scissors-style handles that, when squeezed, push stainless steel points inside the circle.
We all know where I’m going with this.
I’ve used mine twice; once simply to scare my pet, and the other time with a nice gentleman I met at a play party. We each had one in our kit; mine seemed to run a little more smoothly, so we used mine.
Many gentlemen will probably be unable to fit the head of the penis through the circle; however, I found the points worked quite well just on the head of the penis. My model certainly looked scared as hell, which was fine with both of us.