When I was 21, I almost lost several hundred million dollars by threatening to mutilate one of our customers.
In my senior year in college, I worked full time as an intern PM at NetApp NTAP -1%. I spent most of that time at work being groomed and prepared to be a full PM, and given that my background was in cryptography I got pulled into a lot of customer meetings related to security.
One of our customers at the time was undergoing a big change with their security architecture, and I tagged along with one of the directors to the meeting. I was one of ten PMs giving talks on roadmap and our plans, and I had 30 minutes to convince their CIO and CEO that we could integrate our new systems well with the new security infrastructure they were rolling out.