What's the most useless skill you've mastered, and how did you end up getting so good at it?

I am better at helping others flesh out ideas and expanding on them than I am making up my own ideas. I'm good at troubleshooting problems better than most I've ever met. I owe both to PC troubleshooting over the last few decades (from Apple 2e and Pentium II to present). I find that people these days have tunnel vision and focus on short-term gains over long-term payoffs, often to the detriment of future productivity.