I dropped my arm into a 26cc gas motor spinning an 18x6 prop back in October.  Cut all the way through the muscle in my forearm.  Just missed the main nerve that controls most of your hand.  The ER dr. held the laceration open and showed me the nerve and some tendons and how close I was.  Got some good pictures of it while I was there....once they got me doped up on morphine I wanted to see how bad it was.  After a few layers of stitches to put the muscle back together along with the skin, I was out.  Took a fraction of a second to do the damage with the motor running about 4000 rpm.  Thats what I get for not putting my radio in my normal place when starting the plane.  Reached back to get it and slice.  Still had some nerve damage, and still can't feel most of the outer portion of my right arm from the elbow to the wrist but realizing that it could have been MUCH worse makes me ok with it.  It hurts like hell some days but they say it will get better with time and I may get the feeling back in a few months.  Went for a follow-up a couple weeks after and the dr asked me if I wanted something for pain.  My response was "nope, kinda glad I can still feel it to be honest."  I took the accident as a warning that I need to pay closer attention and I thank God it wasn't worse.  It was definitely an eye opening experience.  I was at home by myself, outside my garage in the back of my house when I did it and as I was holding a rag on my arm and hunting for my phone all I could think is if I pass out back here it will be hours before someone finds me and I'm likely to bleed to death.  Needless to say I pay a little more attention now.