I had my microwave under the electric switch for the boiler. I put a chopping board on top of the microwave which turned the switch off without me realising.
No heating or hot water so called the plumber out...took him quite a while to figure out what had happened :-)
FF, my Mum noticed my school collar was sticking up and tried to sort it out whilst I was wearing, I ended up with a 2" blister that looked like a caterpillar :-(
Similar to the u-bend, I lost count of the number of times having loving made a big pot of stock they've strained it straight down the sink.
When you're staying with guests and throw back the bedroom curtains in the morning......do not instinctively try to catch their collection of cacti that you've knocked off the windowsill..... :-(