You do parkour too huh? I like that you've used the right title 
I understand the feeling of dancing between hobbies and interests. Happened a lot with me when I was a few years younger. It kinda settled, but it has its moments for sure. Like, at the moment I spend most of my time gaming...but once it stops raining (if ever) that will switch to more physical endeavours with any luck. Then in the summer, LARP season starts up again, which is the biggest 'thing' I have each year
Hey, freerunning is a totally legit term. It's just got a bunch of superfluous flips and shit in it that I'm entirely disinterested in.
I find that I actually flutter a lot more around different interests as I get older. I constantly bump into things I'm really interested in and then spend a week completely engrossed in whatever it is before I mellow out and do other stuff as well.
I guess my 'thing' is really general: I'm ridiculously interested in languages and everything to do with them, which is fortunate given my studies (I'm studying language technology / computer linguistics). I'm also extremely interested in game design and particularly anything where you play people as well as the rules.
I do programming both as a (future) profession and hobby. On the hobby side, I develop video games and tools for pen and paper role playing games (the latter also is my master's thesis project).
I practice climbing (both indoor top rope and indoor boulder, haven't tried outdoors yet).
Games are my passion, both playing and creating. I play and design pen and paper role playing games.
I also play video games; currently Hearthstone is what I spend the most time on. I also play a fair amount of casual Magic: The Gathering.
Hey I've been meaning to ask you if you have any experience with Dungeon World? My group's Dark Heresy campaign is about to be finished and the GM wants to do a dungeon crawl next, and I've heard really good things of DW. D&D 4e is not an option unfortunately, since the group is too big and would be unwieldy with D&D.
By the way, if you guys are interested in really well made games that emphasise both analytical and social skills, you really should watch the Korean game show
The Genius Game. It's ridiculously well made, and basically Game Theory: The Show.
Fuck it, just watch it anyway.
EDIT: almost forgot, you can find all of the episodes (subbed) in
this tumblr post.