Bjork, at the Union Chapel, Islington, in midwinter, close to my 21st birthday. I'd gone onto her website and they'd just posted that the tickets were available, I got most of the way through the registration process and then stopped because I didn't have a credit card. Didn't think about it again until about six months later when I got a call asking if I still wanted the tickets. I have no idea how this could have happened, to be honest.
The Islington Chapel is a tiny, ornate church in London, and it was lit only by candles, and it was entirely acoustic, backed by the Brodsky Quartet. It went on for over an hour, all the songs were completely new arrangements, and she did a version of Petula Clark's 'Downtown' that brought the house down. It was pretentious geek heaven and I don't think I'll ever top it.
My nose was full of soot when I got out due to all the candles. Yeah, thanks for that, Bjork.