So my wife and I are sitting in the living room, and from the basement we suddenly hear PStsssssssssssssss.........
I (being the big strong man) venture down into the gloom to confront the snake-burgler... only to discover it is the rear tire on my bike.
It just went flat.
I said "That's wierd" and went back upstairs. The next day I went to fix it... the valve stem had a crack in the side (if I pushed on it just right it would hold air, push on it a different direction and it would leak). How the heck would that spontaneously happen? Talk about bizarre. I replaced the tube, since there's no way to repair a valve stem that I'm aware of.
This was a full day after the last time I had ridden the bike.
Anyone have a wierder flat story?
 Before anyone suggests it, yes I made sure to take some sandpaper and smooth the hole in the rim where the valve stem goes through, just in case it was sharp and somehow caused the valve stem to fail.