As an electronic engineering student, our exams were negatively marked. If you got an answer wrong you incurred (-0.25 * $availablePoints). If you didn't answer the question you scored 0. We despised this at the time..

Now a medical student, we don't have negative marking. I feel it's actually very important in this discipline to know your limitations and not pass-off as though you know more than you do. I have however encountered resistance to this, having professors question my very reasons for doing medicine due to leaving questions unanswered..!