Not a huge mystery, but hits close to home to me:
One day, a few years back (not long after we bought our house), I was in the kitchen drinking a beer. My wife called me to come help her with something in the ~~kitchen~~ living room. I put my beer (still half-full) down and went to help her. Came back a few minutes later, and the beer was gone.
We have dubbed this mysterious...thing that disappeared my beer the "beer gremlin."
Edit: fixed to reflect actual rooms involved