First proper software dev job, very naive, tasked to write a 'soft switch' for a well known companies set of production lines, depending on what product was being produced at a particular time. Wrote it weeks before the deadline, forgot about it, night before I had a quick review and realised I had missed half the spec aaaand it was going live the following day. Shitting myself I pulled an all nighter, drove to the office at 5am, managed to get it done with minutes to spare for 9am. To my knowledge it's still being used today. I left shortly after that.