Finally learning, playing, and enjoying a sport - Squash! I have successfully gone from just about 0 activity (aside from walking everywhere - NYC), to playing squash 3+ times a week.
Growing up, I had never had interest (or natural ability) playing sports. Like many here, I'd prefer tooling around on computers, reading, etc. Likely, this became a self-fulfilling prophesy about "not being a sports person".
Well last year, after some thinking of - "if not now, when? When I'm 40?" I went to a gym, bit the bullet, signed up, bought 10 hours of private lessons for squash (first racquetball, but I switched immediately after trying squash once). It is probably some of the most fun I've had in years, maybe decades. Met so many great people, actually feeling fantastic shape for thr first time in my life.
I'm 34, and am actually a "sports person" now. Laughing even saying it in my head. I've used this achievement/habit also to become more of a morning person (by deliberately scheduling games with people at 7 or 8am), and also to do different activities at the gym (e.g. high intensity interval training group classes; running, and even some weight-lifting). It's even propelled me to think more about the food I'm putting into my body, cook more, etc.
If you have never heard of squash, check it out. It's intense (1000+ kcal per hour), easy to learn, low risk of injury compared to other sports, and is often cited as one of the healthiest sports out there. It's tons of fun (even if you're terrible), has a nice long and rewarding learning curve, is very strategic (the chess-like aspect of it appeals to my technical brain), and again - just tons of fun.
A trusted technology friend passed on the advice to try it to me, so I'm passing it on to you all! Try some squashing!