Probably my favorite thing to do is ride dirtbikes/quads/snowmobiles. Although I only have a snowmobile at the moment, but I wish wish wish I had a dirtbike. I miss my old one so much. :'(
I was into R/C for a while. I had a HPI Savage nitro monster truck, which was really fun to mess with, but also pretty expensive. I sold it (as a roller) because I blew the motor and couldn't afford to replace it, and figured it'd just sit there forever. I got a little money out of it at least.
I also really enjoy BMX, fishing, and anything outdoors really (which you might find hard to believe, cause I sit on the computer all day...but yeah).