First professional job, at an oil refinery that at the time had an impressive no workplace injury record - two years and counting, or something like that. I worked in an admin building outside the main refinery operations, but occasionally had to drive over to deliver reports. On one of my first months at work I was doing this and had pulled my car up to the laboratory building but left it running. After I got out I realised I hadn't put the park brake on. I got back in the car and put my foot firmly on the accelerator instead of the brake, running the car into the building. There wasn't too much damage but it made a loud BANG and a bunch of people came out. If I'd been hurt and ruined the entire company's safety record for such a stupid, trivial incident, they probably would have quietly disposed of me.