Some years ago I posted a video where a guy was nailing his testicle, just in the centre of it. Maybe you are interested in something that mean Miss Venus? I am not sure if this would couse a permanent damage. Judging from my self, using sterile needles to scew them, was safe enough. But a nail? hmm sounds interesting, even for me to try (not by my self though... if a woman is going to do it OK)
http://www.femaledom.com/forum/showp...&postcount=112