Don't have one, but I understand them as an artistic effort to define identity. Jenny has one: a little ivy wrap around her ankle. Kinda sexy, I think.
Myself: I don't have one, don't really want one. OTOH, I have two factors which make tattoos redundant.
1.) I've already got so many scars on me that I need another mark like a [new] hole in the head. None of the scars are intentional (self-mutilation kinda weirds me out), I've just lived a lot of life and endured a lot of injuries.
2.) I used to lift. I was a gym rat for about fifteen years. It may not be ink, but it was a conscious effort to modify the appearance of my body. Can't hide that underneath long sleeves or a high collar. You have to deal with a completely different set of pre-judgments, some convenient, some sad.
But I guess if I had to get a tattoo, I'd put my blood type and the words "organ donor" on the underside of my wrist (under my watch band).