I wrote (in perl) what I thought was a quality assurance tool to see how many gift certificates were being used by customer service reps and what size and in which cases. It wasn't an assigned task, but it was related to my group and with perl it was the kind of thing that could be done in an afternoon so I did.
While my goal had only been to ensure service quality, it ended up, as you probably already guessed, turning up quite a bit of fraud. A few service reps giving away thousands of dollars worth of gift certificates in total to friends/family.
A small batch of firings ensued.