Just a couple of weeks ago, right here on FR, somebody posted a story about some idiot in Moscow who had bad paint stains on his pants...so he decided to add a liter or so of gasoline to the wash.
KAH-WOOOOM! Blew out all the retaining walls in his apartment, among other things.
Many years ago my cousin opened the nozzle of a propane tank on the ground. He then struck a match to see if it would burn. It did! Fortunately, he was not too badly burned, but he never did it again.