When I was 15 my friend persuaded me to get a tattoo and a piercing with him from a guy he knew. As we were underage we got them where they couldn't be seen. Can live with the piercing, but wish I hadn't got the tattoo.
It seems a good idea at the time when you are quite young, but might regret even more when you're older because old men (unless they have been in the Navy,say) and women for that matter, look awful.