I may have to think on that one for some time. I'm not a very spontaneous type of person. Ahh, I think I have one.
It was when I had my ears pierced. I never wanted them pierced and still don't wear earrings much these days. But I was in my late 20's/early 30's when my ex and I had been quarreling. I went to the mall just to calm my nerves when I saw they were giving away free earrings with a $10 piercing. I don't know what came over me, but I just walked up and had it done. I still can't believe I did it, what with my fear of needles and such (in my mind, posts and hooks still represent needles). But there you have it, I did it and it was very spur of the moment.