Dancing would be my second choice.
I'll have to go with drawing. I used to paint and draw until my Freshman year in college before life got in the way and ultimately stopped me from going further with it. I never made it to the level I wanted to be at, though.
Sometimes it's hard putting your thoughts into words, and being able to paint or draw them can be a better way of expressing yourself. I have a pretty erratic imagination at times, and I sometimes forget my train of thought, so being able to give these thoughts and ideas a physical presence is a fun way of expressing myself.