If I get too dehydrated I completely lose my sight. I mean I cannot see a damn thing, it just sort of dissolves away until I'm blind. Believe me, it's not a good thing to happen in the middle of a mosh pit. Usually sitting down sorts it all out until I can get to some water. Didn't really fancy sitting down in the middle of a mosh pit though, I pretty much fought my way to where I thought the back was...
I also once had a sinus infection that somehow turned my snot bright orange. Boy was that weird. Also pretty disgusting...
I also have pretty dodgy circulation in my hands and knees, though not as many people notice the knees, covered up by jeans as they are. My hands will regularly go purple even when I don't feel cold. Sometimes they go grey, and sometimes they go both grey and purple, with small random spots of bright orange.
Might be something to do with the fact that I'm 6'5", and weigh 9 stone. People often hate me for that fact
Edit:
Remembered more!
10 weeks premature, sadly not so wow inducing as face_down, but still pretty early.
Used to suffer from what I believe was Labyrinthitis, happened 3 or 4 times a year for about 11 years, started when I was 5. Thankfully havn't had it for a few years now, but it really was horrible when I did get it.
It would last 1 or 2 weeks at a time, I would get vertigo, I would be very unsteady on my feet, and whenever I tried to walk around, I threw up. Absolutely horrible, I wouldn't wish it on anyone.
There's probably more, but I can't really be bothered to think right now.
Thought about it a bit more:
My absolute weirdest thing is that I am right now spending my time writing about my weird things on an internet forum*. Just seems kinda weird to me.
*Sorry if that joke's already been made, I'm tired and don't really want to read through the whole thread.