I haven't been able to decide on one. I wish they would only last a few years, not forever!
I have considered getting "Love as thou wilt." from the Kushiel's Legacy series. I've been thinking about it for a few years, but I don't know if I'd actually like how it looks forever.
I was thinking of getting a heart with wings after Puck died, but I am not sure I want to mark my body ever time somebody I love dies, so I will wait a while to see if I still want it. I've been wearing his memorial pendant, which works for me.
I have my ears pierced, but I almost never wear earrings because my ears get irritated easily, even with "sensitive" earrings.
I have my belly button pierced, and I leave it in all the time. It took a LONG time to heal, but as long as I leave in, it's fine now.