So my pick is sales. When I was presenting my thesis to the assessor, he was unimpressed. It was a bachelor's thesis, technically simple, but it attacked the problem from a different angle and had better progress than some PhD students working on the same project. My supervisor congratulated me on the presentation. I told him my assessor wasn't as impressed. He replied, "Maybe you didn't sell it well enough."
Since then, I got a little obsessed in finding out how to sell things better. A lot of people get the wrong impression of sales. They think it's an overdressed guy trying to put their foot in the door and promise anything for a sale.
Sales is simple. You have something that someone wants. Something other people wish they had and probably even spent a lot of money trying to patch themselves. They would happily part with money to get someone else to handle it. The trick with sales is to simply to find those people and explain your product in such a way that they throw money at you. There's no need to be good with words or be charismatic. Just explain the product well and explain why it's worth it.
It applies to many other parts of life too - getting a job, getting a date, hiring, pitching for a startup or scholarship. The first step is understanding what you have and why it's better. The rest is just articulating that well.