Put a small hole in my eyelid changing strings. I was bringing a string up to pitch and it caught on the barrel of another tuner, whipped around and caught me in the eye. Fortunately, my reflexes must have been good and I closed my eye in time. Now, I have to wear glass to see what I'm doing in the first place, so the danger is less. I'm still very aware of what's happening with that string end, though.