Heh, my first job as a rookie was helping my friend's dad, the builder who gave me my first job, build a really gorgeous sunroom on a lake house. I made it through the rough, roofing, and siding unscathed.....not so the finish.
I went to lunch when I was in the middle of casing a window and got back, being full of enthusiasm for this job I REALLY loved wanted to jump in and get right back to work. The boss had this ancient brad nailer, no safety and a vacuum cleaner belt to hold tension on the feed slide (definately not an OSHA approved tool) and when I went to reload it, forgetting to unplug it from the air hose first, was bracing in against my body to stretch that damn vac cleaner band and must have raised a knuckle just enough to hit the hair trigger.
I felt a tap and looked down to see my shirt was now nailed to my chest...LOL