I think tattoos are cool, but I could never get one. For someone like me who changes his mind as often as I do, tattoos are just too permanent.
Some of my illustrations have shown up on skin however. People send me pics of their finished work and I wonder if I shouldn't get some money for that. (: Seriously, it is the biggest compliment to have your work permanently etched into someone's skin.
I did work on a tattoo commission once though. This is the sketch. Thankfully the client decided against it.