I was getting impatient while grinding down a 1/0 ring terminal to fit my alternator positive terminal. I was using goggles (small bits of metal flying around). I had just a little bit more metal to shave after the last test fit, and I didn't put the goggles back on, figuring I'd just make short work of it. You guessed it - small bit of metal came flying up and nailed me, luckily in the eyelid, but enough to cause bleeding. A couple centimeters more and it would have been the eye.
New meaning for 'It's all fun and games until someone loses an eye!'