What's the stupidest thing you've ever done?

Aged about 8 I thought it would be a really good idea to run down the side of hay bluff... I ran about 100 yards flew 600 and faceplanted in a bog at the bottom. Never run so fast before or after.

Running down big hills/mountains is never a good idea...i made the same mistake in Wales on a geography field trip...only took about 4 steps before i was running faster than the billion dollar man....tried desperately to dig my feet in sideways....eventually managed to slow down to an almost stop only to have my friend who made the same mistake plough into me from behind and send me running off down the hill again...thought i was gonna actually die :)