I have one that still creeps me out and no one really has explained it to me. It has been a mystery for DECADES.
It was a regular Monday where my uncle worked. It was a quiet office, filled with cubicles where people clocked in and people clocked out. However, part of his regular work day for included playing cards during lunch with co-workers. It was a four person game, so three of his coworkers were also present in the lunch room. Though it was a regular lunch day on a regular work day, he was irregularly quiet. After about 30 minutes of playing during lunch, he stands up to go to the restroom and never came back.
No one thought any different, no one bothered to check where he was, soon enough it was time to clock in and go back to the cubicles.
Later that afternoon, my aunt calls my uncle's office, crying. She was calling to inform his co-workers that Uncle Bert had died of a heart attack over the weekend. Three different people in the office told the same story that they had been playing cards with him. Until today, we have no freakin clue what the hell happened that day.