I would say, in my last corporate job, I worked with two guys I would consider mentors. Many years ago, I was being looked at for a promotion, though I didn't know it at the time. We were in the middle of some major acquisitions and reorganizations. One of our corporate VP's spent about 6 months raking my ass over the coals on a regular basis as he reviewed my work. Two of the most frequent remarks he made during his visits were, "Do it this way! Do I have to explain it?" and "Clean your desk! Do you need that pencil out now?" or the equivalent. He had been Special Forces in Vietnam, which somewhat explains his style. When the dust settled I got the new job, and my new boss said, "I'd say I'm sorry about the training, but if you want to see what someone can do, you put their ass on the stove and turn up the heat."

The man I consider my second mentor; I worked with in several different branches and departments over a period of roughly four years, and he taught me that often, you can get better performance from your subordinates by quietly telling them your expectations than kicking their balls up around their ears when they fail. So, I came around to the realization that often subordinates fail because their manager hadn't clearly defined his expectations and provided enough feedback and direction. Though I always had employees who benefited from a swift kick to the nuts on occasion.