Well, stories don't get much worse than this. A 14-year-old boy in China was killed when his chair exploded, sending chunks of metal into his rectum. The bleeding this caused killed him.
The alleged explosion came from the gas cylinder that was in the base of the chair, the part that allowed the user to adjust the seat up and down. The canister gets compressed when you sit on it, but can it actually create enough energy to make the seat cushion explode like that and kill a man? I doubt it, but this is what people are reporting.