The biggest fail I've done (so far...) happened summer of 2011. I was painting pipes out in an oil field when I got to a pipe about 10' above the ground. So far everything is pretty routine, I just grab a nearby ladder and set it up. The problem was that there was a raised area below the pipe, so that the left leg of the ladder was 6" off the ground. My genius solution was to put the ladder on the closest flat ground to the pipe! which means that the ladder is now set up at a 45 degree angle. When I climbed up and started painting the ladder inevitably slipped, and my thumb got pinched between the rung I was holding and a washer on the pipe. Took out a chunk of my thumb at the base of the nail (I got lucky with a glancing hit, a direct one might have cost me much more). Fortunately the worst damage was to the nail bed, so the only lasting damage is that my nail doesn't grow properly