Twice, in two separate jobs.
The first time, about 20 years ago or so, I was working for a commercial roofing company doing hot-mop. The foreman sent me down to run the asphalt kettle while the regular guy was on lunch. I asked for the face shield (the normal guy didn't wear one) and was told that we didn't have one. One of the lugs had an air pocket in it which exploded as I put it in the kettle and sprayed hot tar onto my face and arms. Luckily I was wearing sunglasses which protected my eyes. Turns out the face shield was in the cab of the foreman's truck, he just didn't want to get it out. The foreman lost his job (I had to push for that to happen - at first they just wanted to write him up), and I moved on to something else shortly thereafter. To this day, I can't stand to be around road construction for any length of time. The smell of hot asphalt makes me nauseous.
The second time was in the trucking industry. There were 6 drivers who covered a two state area, and the dispatch manager was mangling the routes so badly that it would take us an extra 45 minutes every morning to sit down and trade out stops and load sheets so that everything went on the truck it was supposed to be on. Of course, he went out of his way to make sure that the downtime was blamed on the drivers being lazy rather than on him being an idiot. We put up with it for about a month while trying to explain our routes to him before we collectively went into the regional manager's office and explained that if the dispatch manager didn't go away we weren't going to run the routes anymore. He was called into the office and fired in front of us, at which point he started screaming at us and asking us why we hated him.