I realize this is a broad question, but my life has changed drastically in the last few months, and I'm looking to experience more before I get too old. I know the usual answers like getting married, having kids, and so on.
I'm more interested in skills, hobbies, fields of education, practices, habits, and experiences that have shaped (for the better) the person you are today.
EMT
I'm a bit of a prepper so I've always been interested in first aid skills, but I had no idea that an EMT cert could be obtained so quickly!
Skydiving, scuba, rockclimbing, caving, motorcycling
It's funny, I've gone sky and scuba diving, but you couldn't pay me to get on a motorcycle. I just know I'd wrap myself around a lamp post within the first week. I like going fast a little too much.
Weed
I spent a couple decades as a daily smoker, and I'm definitely one of the lazy ones. Even so, I attribute much of my lasting outlook on the world to marijuana and the friends I made while smoking. A positive experience overall.
Basic carpentry.
+1. I love to make things, even though I'm a notoriously bad craftsman.
Shooting.
Couldn't agree more. Little in life provides as much peace of mind as having confidence in your ability to operate a firearm and defend your home.
Becoming an EMT (emergency medical tech) and driving an ambulance as a volunteer. The EMT badge was not hard at all, just one semester, one or two nights a week, plus a little hospital time. You get to see a slice of life you'd never otherwise see, you get to drive fast and be a good guy. Totally worthwhile.
Skydiving, scuba, rockclimbing, caving, motorcycling - all of these things are more accessible that you might think. They all demand calm and care, qualities that serve you well anywhere.
Weed. Seriously. There are very few things that you can experience as an adult that are safe, pleasant, and totally unlike anything that you have experienced before. It won't make you lazy unless you're already that way.
Basic carpentry. Nothing fancy, just the ability to put together useful things in a sensible way. You can get fancy if you want, but don't let the complicated stuff hold you away from the easier things.
Shooting. It's fun, and it can be taken seriously as a defensive skill too.