You are given the option to instantaneously master one single skill of your choice, which skill would you choose? And what would you do with it?

You are given the option to instantaneously master one single skill of your choice, which skill would you choose? And what would you do with it?
I would pick European football (or soccer for the fellow Americans), then I can join big clubs and earn tons of money
@north_flag this is a good point, the OP said you'll master the skill, so you should become one of the top players of all time
I'd choose boxing. Good for the body condition, self defense and a great sport overall