I heard beeping that sounded like a malfunctioning smoke alarm. (It wasn't, but more on that later.) I asked daisy_knotwise to grab a 9V battery so I could replace the likely offender, but when I couldn't figure out which smoke alarm was complaining, I ended up dropping the battery in my shirt pocket and forgetting about it.
Until about ten minutes later, when I noticed that something was really hot in my shirt pocket. What the?!
I grabbed the very, very hot battery out of my pocket. I carry my wedding ring there and it had shorted across the battery terminals. The ring was nice and toasty warm too.