I've had a couple of episodes, the first was when I was at work (at Burger King, go on, laugh it up, I'm a supervisor of a government quango now). I'd been feeling almost drunk all day, but I hadn't had any alcohol, then suddenly I just remember just feeling so dizzy and my head was spinning, next thing I knew I was in an ambulance. Someone stole my hat when I fell :\ I mean, how terrible is that, someone faints, potentially might be dead, and instead of helping them "Hey, cool, I got me a BK cap!".
I had tests and stuff afterwards because I'd been perfectly healthy with no family history of fainting, and they could never put their finger on an actual cause so put it down to some form of epilepsy (which is stupid if you know how many hours I've spent inches away from every flashy seizure inducing video game you can think of).
The next time anything happened I was actually in bed asleep, so I don't know if it counts as fainting, but I was with my boyfriend and apparently I must have had some kind of seizure while I was asleep. I've never had anything apart from those 2 instances, although recently I've been getting random dizzy spells for no apparent reason... Oh well.