I think belly button piercings are hot because you don't know they are there until you actually get physical with the girl & then you are like, "Wow!" I just think it's sexier than any of the other piercings that you can see. I think it would totally turn me on during sex if my girl suddenly got one and we were making out and I found it - especially if I know she did it just to turn me on! I don't think I'd be as turned on with the nipple piercings though. I'm also not really turned on by having a girl's "private" area pierced. I just think that would be kind of weird. Those are just my thoughts anyway! :)
Ears, hands down the hottest(not on list), belly button ring or that little golden ball(stud?) looks very sexy too.
You didn't mention tattoo's but I have to mention this, I absolutly hate tattoo's on women especially the tramp stamp on the lower back. I freaking hate that trampstamp.
lip - I just think of how it could get ripped tongue - I just think of it getting stuck between gap of front teeth nose - could be ok but no good with a cold :P