Go on, guess...
A can opener.
Go figure.
There have been a number of instances where all food preparation came to an abrupt halt due to the lack of a can opener. However, sometimes it's too late to turn back. I came to that realization as I was cooking some ground chicken in a pan and turned to grab a can of pasta sauce. I groaned inwardly as I had absolutely no way of opening the can. Luckily, I had a bottle of balsamic vinaigrette. It was definitely an exercise in creative cookery, but I managed to make a palatable meal of it. Let's just say I made a trip to the store the next day.
"I wake up every evening with a big smile on my face, it never feels out of place, and you're probably still working at a 9 to 5 pace, I wonder how bad that tastes..."