I was 17. I was in Gullane in Scotland working at the British Open. I was staying with a friend in her house up there, and another girl was staying who I'd never met. Over the course of the week, we got to know each other. We spent our last 4 nights in Gullane in the same bed. 1st night was 'first base', 2nd night was 'second base', 3rd night was... well you can guess what it was by the 4th night.
It was great. I'm still friends with the girl, I wasn't drunk, it was in a bed, and I have no regrets.
I can't remember if I've already posted in this thread
but I was 16, within a few days / weeks of being with my boyfriend (I had, however, pined after him for 3 years and I don't regret a thing)
Mine was when I was 15 but with someone who I really loved (still do...but wasn't that long ago...) and someone who i knew i could totally trust- thats why I don't think i will ever regret it because no matter how/if we split up, I know that it was the best way I could have lost it.