About 15 years ago I was on a motorcycle ride with six other guys (and my wife) almost all of them relatively intelligent. Guy riding the brand new, Triumph Speed Triple gets a flat, and has no repair kit. Lucky for him he's with five other, well prepared riders. Friend gives him his repair kit which consists of a hole reamer, rubber plug patch, cement and a small CO2 canister to fill the tire. Oh, and it's about 103 degrees out this day.
Found the leak, reamed the hole, applied cement and inserted plug. All O.K. so far. Victim asks if anyone has a knife to trim the plug. I carried at that time a large CRKT Apache which I use for everything (including scraping wallpaper, stucco, reaming out holes in various materials, and occasionally cutting) so I wasn't too worried about it. I do however keep it ALWAYS shaving sharp. So I throw it to him with the warning, "be careful, it's very sharp". Long story short, he tries to saw through the rubber plug and it instantly travels all the way through the rubber coming to a stop when it reaches the bone of his index finger. He falls on the ground and starts producing blood at an alarming rate. Myself a firefighter / first responder and another guy who is an EMT with a med kit apply first aid and get him laid down in the shade because now he's woozy from the "shock". It's now some 45 minutes later and he's beginning to feel well enough to finish the tire repair, which is all of airing up the tire with the CO2. The CO2 canister has this flimsy little rubber hose for connecting to the valve stem which waited until the tire was just about filled before it exploded off of the stem and into our geniuses now injured finger, causing him to roll around on the ground some more in agony and despair. I make no apologies for the ignorance and knuckleheadedness of people who injure themselves with my cutlery, and I told him so. The trip ended without further incident, but we still talk about it today.