Dude, I feel you man... The same thing happened to me once, but back in 4th grade... So me and my friends are just playing a little game of tag, and as the 'it', it was my duty to tap on one of my friends. Just when I was about to tag my friend, I literally slipped by accident, and it felt like a SLEDGEHAMMER! Man, I'm never gonna forget that memory *shudders*