I've got a navel piercing; I got it done spring '94 (I got out autumn '93)... I liked 'em, and I don;t think we need a degree in psychology to figure out the rest, do we? My body. My life. My belly button. Lick my ring.
It didn't hurt; got hurt once when I humped a stack of crates up some stairs, and rested them on my belt buckle whilst opening a door, but it cleared within a few days.
I like the fact ten years on when 'everyone' has a piercing that my navel piercing is still unusual (for a straight guy).
I had a tragus piercing.... had to take it out as even in liberal Holland (hah!) some people think that what's in your ear counts for more than what's between your ears... morons. Seriously, I've been to the 'States with hair down my back and a tragus (the little triangle of flesh in front of your ear hole) piercing on business and people have not blinked (or have done so behind my back); I now have shorter hair and look way more respectable and my boss still didn't want it; dumb Dutchman.
Oh, that hurt to get done.
Nipple stimulation doesn't do it for me, so piercing would be entirely esthetic and I like mine as is.
I don't get the endorphin thing; I've got a high pain tolerance but when I feel pain I want it to stop.
Some people really gets the endorphin thing; some (not all) people with piercings do, as does any masochist. It's funny; I remember in the Yearbook about WWII I read (when I was 4, appropriate reading material NOT) about some sisters getting beaten on the buttocks by the Nazi's. Apparently they thought it was a miracle that after a few blows it stopped hurting as much.
Anyone whose ever had a recreational beating can tell you this is WHY some people find consensual sadomasochism fun; you can get high as a satelite on your body's own drugs. First few cracks of the crop may hurt, but if you're with someone who is reasonably competant they can build you up slowly...