Worst injury as a kid: When I was 13 I cut my thumb to the bone trimming flash off a metal skeleton with a blunt blade and cut towards myself. That required four stitches and I bled like a split pig when I did it.
So kids, that advice about not using blunt blades and always cutting away from yourself is worth taking note of!
Most painful injury: A few years ago I was creosoting my parents fence. I was on a ladder and I was getting a bit overconfident about how far I could reach with the brush (I was getting fedup of moving the ladder a few inches every so often). Anyway I lost my balance and fell backwards onto some bamboo stakes that were holding plants up. Luckily I wasn't impailed but I had a fair chunk of my back gouged out. I was in agony for weeks with that.
Most embaressing injury (whilst drunk): I was about 17 and like most 17 year olds I loved beer and attempting to impress women. I was rather the worse for wear in my then local and I proclaimed to the pub that I could touch the ceiling with my feet if I jumped off the pool table. My then girlfriend, her friends and the rest of the pub cheered me on (barstewards the lot of 'em!)
Anyway, once I regained conciousness in casualty (A&E for your US types) I was told that, no, I hadn't managed to do what I set out to.

Apparently I'd jumped backwards, flinging my legs in the air and smacked my head against the pool table as I fell to the floor and knocked myself out.
Still I can't complain, the following week the regulars bought me beer all night!
Most stupid injury: A couple of years ago I was having a shower and I slipped and cracked my head against the taps as I went down. That was when I discovered that casualty don't normally use stitches anymore and they superglued my eyebrow back together. I also ended up with a very impressed black eye from that injury as well.