if my (albeit old) memory serves me right, the B707 crash landing short of Paris in the late 60s was caused by a lavatory fire from a cigarette
A common piece of folklore. From:
http://aviation-safety.net/database/1973/730711-0.htm
PROBABLE CAUSE: "A fire which appears to have started in the washbasin unit of the aft right toilet. It was detected because smoke had entered the adjacent left toilet. The fire may have been started by an electrical fault or by the carelessness of a passenger.
And before anyone suggests it, the Air Canada DC-9 at Cincinnati was an electrical fire.