Depends on the mood, on the environment. At work or when I'm working, something that I can't sing, so I don't lose concentration. In the car, something that I can sing, so I don't fall asleep. At parties, the usual
I'm a huge fan of orchestrated music, Classical or otherwise. I enjoy Rock or Metal occasionally as long as it has a symphonic element to it (ie. Nightwish). I enjoy a lot of movie soundtracks also, it's a very inspiring type of music for me. Mainstream pop/rap/rock has never appealed to me, for the most part it's dumbed-down, recycled, media machine-driven garbage.