I love this question. First and foremost, meditation. It definitely helps me be more present. Another skill that gives me joy is reading. I can concentratedly read for 2 hours, but after 2 hours I need to take a break. I can't think of any other activity that I can concentrate so long on. Ideally, I would become a scholar but I'm going into software engineering for now:)

Reading, writing, coding (usually debugging, once I have a consistent and smooth repro process), lifting.

I've been painting some walls in my house recently. After getting over the short learning curve of making a mess everywhere I find it pretty therapeutic and meditative.

Listening to music. Flying an airplane. Doing a hard workout. Building a Lego set. Fixing something with my hands. Cooking (trying not to cut off any more finger tips).

Coding, video games, listening to music, painting.

And long time ago when I used to run, running.

Refactoring legacy code.

Coding, solving math problems on paper (equations and stuff)

drawing.

Thank you for sharing the wiki link, I learned something. I like drawing, it let me forget about other things for hours. I use it as a therapy for anxiety.

Ultimate frisbee is a "flow" kind of game.

Bouldering, meditating, ping pong

Machining, making gears.

coding, skiing.

running