I really like computer programming. I'm trying to become a computer programming guru, but there's a hell of a lot to know (and it's not all available in books yet, either). I program computers at work, and I get paid to do it. I program computers when I'm not at work, and don't get paid for it. I pay a price in hand/finger strain, weight gain, and social isolation, but I reap the benefits of becoming really good at computer programming. :)
Linux running Apache webserver with a MySQL database and PHP scripting to tie it all together. I build educational web apps for Insight Learning Technology, Inc. and learning experiments for the UCLA Human Perception Lab.
MudOS and LPC
I'm a volunteer programmer (called 'creator') on New Moon Mud. A 'Mud' is a Multi-User Domain (or, more traditionally, a Multi-User Dungeon) which means that a bunch of people can connect to it over the Internet and play together. New Moon is Free (as in Beer) to play, but in order to look at the source code you have to be invited to become a creator.
I've developed an entire area of my website to New Moon and things related.
Despite 9 years of training, I'm no expert. More than half of that time has involved me recovering from injuries suffered on or off the mat. Despite the obvious dangers, I plan to train until I'm no longer able to.
Krav Maga is an Israeli method of self defense. It's essentially a survival attitude, some escape moves that build on people's natural instincts so they're easier to teach to noobs, various weapon defenses, and then the gamut of unarmed combat options used in MMA. It's not MMA though, because they're always reminding you that you're allowed to fight dirty if your own survival is on the line.
Brazilian Jiu Jitsu
Brazilian Jiu Jistu is a wrestling discipline which can be differentiated from other wrestling disciplines by the emphasis on using your legs to control an opponent atop you.