user6 Microsoft Excel, especially functions. So many jobs want this, so many people can't do it, and they will love you for it.
I second this. Excel is one of the most used tools in business and most companies now try to hire people with a sound knowledge of the program.
Another skill that's easy to learn and can help impress your friends, is the moonwalk! ✨🕺
It's actually not that hard at all. All you need to remember is that you're going to have a straight, stiff leg and a bent leg the whole time. One is going to be straight, one is going to be bent the whole time. Enjoy this video tutorial on learning how to moonwalk and good luck!