Spontaneous human combustion
Spontaneous human combustion is a weird phenomenon that nobody will insure you against.
There are never any witnesses. Victims are typically old and fat, and are found in a chair or bed partially or completely burned to ash. Whatever fire that was failed to spread beyond the immediate location of the body. Investigators like to joke about people with "volatile personalities" but they're not the ones that have to clean up the mess.
Smoking has been ruled out as a cause in many cases, as is drinking while eating flaming skewers of meat. Fire experts point out that badly stored pistachios can spontaneously combust. But how gangs of little tiny pistachios were able to break into a frequently locked house or room remains a mystery.
See and smell