Fair warning: I am a pretty big nerd/geek, but I wouldn't say I'm obsessed with anything, I merely enjoy spending my free time gaming or reading, etc. Of course I'd rather be with friends than "geeking out." I like playing video games, reading, watching tv (especially hockey), going for a walk on a sunny day, going to the beach, having adventures, and hanging out with my friends, along with a multitude of other things which I can't think of at the moment.
Movies: Man, I love a lot of movies. Serenity, Iron Man, LOTR, Scott Pilgrim, Star Trek, Star Wars, Bruce Almighty, Casino Royale, League of Extraordinary Gentlemen, V for Vendetta, Fight Club, Zombieland, The A-Team, Doctor Horrible's Sing Along Blog, a lot more...
TV: Firefly, How I Met Your Mother, The Big Bang Theory, Entourage, Castle, Community, South Park, Game of Thrones, Star Trek, Star Gate, Doctor Who, Breaking Bad, Futurama, It's Always Sunny in Philadelphia, Wilfred, Adventure Time are the main ones.
music: I'm not too specific about what music I listen to, but a few bands are: Weezer, Said the Whale, Mother Mother, Metric, Electric Six, Johnny Cash, Taylor Swift, Cage the Elephant, Flight of the Conchords, Lady Gaga.
There's no Video Game category, but there should be so...
Video Games: Halo, Skylanders, Skyrim, Fable , Pokemon, Zelda, Final Fantasy, Mario Kart, Monster Hunter, Metal Gear Solid, Red Dead Redemption, Batman Arkham Asylum/Arkham City, Mario, probably more I'm missing.
and last but certainly not least, my mental faculties (I don't think I could stand being senile.)