I'm only on page 3 of this thread, but I've got one. At my first cashier job one of the managers was arrested for stealing. I was working the front register when a uniformed police officer came in and asked me where this particular manager was, and I said that I thought she was probably in the stock room. He thanked me, and went back. I didn't think anything of it until I heard from another employee that she had just been led out in handcuffs. It turns out that she had been stealing money from the safe for some time, and one of the other managers had finally caught her in the act and called the police.
Needless to say, she was fired. She was actually the one I got along the best with, which had me questioning my instincts.