That I've almost burnt my house down.
Last night, I left oil in a frying pan, with the flame fully lit as I did the dishes, and I think I even watched a bit of TV. It was only when I was preparing to go to bed, that I turned out the lights and saw that I'd been heating the oil for at least 2 hours !!!
This morning, I left my George Foreman grill running, and went to work !! I thought I'd forgotten to turn it off on my way to work, but I was already running late. Got home at 7pm (11 hours later), and lo and behold, there is was, heating away.
So that's a spike on both my gas bill and electric.....