What's a skill that's easy to learn but makes you seem like a genius?

Google. Seriously. Learn how to quickly and efficiently use Google to look up the answers to problems, especially IT-related problems. It's stunning how many people are completely inept at this and, when they ask you to solve a problem and you do so simply by Googling it, they think you're a genius. I'm an IT guy, and a ridiculous amount of my job is Googling incredibly simple problems, applying the incredibly simple solutions, and literally being told by my client that I'm a genius. The inverse is also true. The more difficult and time-consuming the problem is, with vast amounts of time, effort, drawing on past experience, researching, working with third-party support, etc. it takes to solve it, the LESS likely they are to be impressed with the work you put in and are more likely to be annoyed that this should have been simple and taken five minutes.