How about one from the perspective of the teacher?
I knew that there were some students who were going to take advantage of the multiple choice final that I was giving. I cut out a bar code from something and photocopied it onto the first page of the exam.
After handing out the exam I made sure to announce that they should check and double check that the number on the bar code matches the one on the answer sheet or it will be graded with the wrong answer key.
Oy, you should have seen some of those faces, I felt so bad for them.