In terms of playing, jazz is my favorite music, especially in a smaller combo setting. The freedom in improvisation is AMAZING! I would jam with people all day on jazz if I had the time (or all the people to jam with). My main jazz instuments are alto sax and piano.
I'm not exclusively a jazz musician though. As a performer, I play sax, piano, bass clarinet, and am sort of learning guitar, and I kind of mess around on some other stuff. I've composed for a year and a half, mostly on a computer, but for some smaller scale performance works on piano and pen and paper (and I find both to be equally musical); a vast majority of my work is orchestral. Actually though, back on the jazz topic, I've been writing some jazz stuff recently, and been enjoying that a lot. Heh, I'm pretty much cool with most music.