What are some inconspicuous piercings?

I've had my ears/cartilage, nose, and belly button pierced so far, but I want something new. I've heard that tattoos are addicting, and I think piercings are the same. However, I work in a store that doesn't allow too drastic of a piercing. So I was wondering if anyone has ideas of what I could get that is unnoticeable or completely hidden. Oh, and I'm female if that helps...and no genital piercings, I'm just not too crazy about those! Thanks!