The Trifle Incident! 
Ex DH and I had not been married long, and were both very partial to M&S fresh cream fruit trifles, and would eat a large one each
.
I had a day off, went shopping and (along with other stuff) bought 2 of them.
Spent some time doing the usual domestic stuff, but the trifle kept calling to me.
I could stand it no more, so ate one of them.
Worried that my sin would be discovered, I removed half of the contents from the kitchen bin, put the carton in, then replaced the rest of the rubbish.
When Ex DH came home, I told him there had only been one in the shop, so made him share it. I was even mean enough to demand that I should have the cherry from the top!