I had quite a lot of fun in the Army Reserve in England (6 Rifles, B Company) while I was a teenager (17.5 - 19.5). Being paid to spend my weekends running around a field, camping, and shooting was a lot better than alternatives like working in a shop. I do partly regret not joining a deployment (some of my buddies went on Herrick XIII) but I still toy with the idea of rejoining in the future so maybe one day.