This is a fun one!!  I'm about as accident prone as they get.   Broken bones, sprains, stitches, pulled muscles, dislocated fingers etc, but my worst sports injury was due to my own stupidity.  I was 19 years old and in the middle of a heated softball game!  I had an asthma attack, but decided I could continue playing without my inhaler.  I was extremely lightheaded, but stubborn as can be.  While playing first base, I was stretched out and ready for the double play, when I just stopped breathing.  As I'm falling to the ground, the ball just so happened to catch me right in the eye.  The end result is this.... Eight stitches and several hours in a hospital... eesh.  At least it looks pretty!