I got my navel pierced and a tattoo on my chest as a kind of "rite-of-passage" thing to symbolise my becoming an adult. I haven't tasted alcohol yet, but that's purely my choice. I should probably point out that I spent the rest of my birthday in a fair amount of pain, feeling weak and sick and just wanting to lie on my back to alleviate it. Just in case you might want to try the same thing.
when I turned 18 I legaly bought my first r rated movie (where I live we're not allowed to buy these movies till we're 18)... and it was pretty boring. Before I was allowed to buy them it was always exciting if I could get through with it or not.