Nipples are probably my favorite pierce on other people. There is just nothing like licking someone's nipples when they have rings in them... :)
For me, they also served another purpose. My nipples had never been the most sensitive things, but getting them pierced improved the sensitivity quite a bit. There was also a cost. For me, these were perhaps the most painful of the pierces I've had done. It was really interesting:
The guy at The Nomad told me to lie down on the table (paper covered doctor's variety.) I did. He marked the entry and exit holes, and grabbed the needle. He started pushing it through. I closed my eyes against the pain. I had expected it to hurt but WOW. By the time he was done with the first one my back was arched, I was sweating, my eyes were sore from squinting.. It was quite an experience.I was (and still am) very happy.
Then he reached for the second needle. I whimpered :)
I got up after the second one was done, pulling the paper off my sweaty back, and sat up so he could my eyebrow.
After everything was done, I walked out to pay, and there were three hippy girls that had been there when I walked in. They smiled, and one said "Look! It's a happy boy!"