I'm not sure that people pick extracurriculars for the skills they develop, but I think this is a good idea to help people who might be in a similar job and have a hard time putting their finger on what skills they've been building. I'll add one from back when I was in high school:
Religious School Teacher's Aid of pre-K through middle school students - supported teacher's lesson plans, and students' content-area and social-emotional learning - coordination with colleagues, conflict mediation and resolution, fast-paced environment, patience, leadership, innovation, breaking down concepts to teach to others