Nature
Nature and landscape photography has always been something I'm drawn to. Often, for me at least, taking a landscape photo consists of some form of adventure. Whether it's a small local "adventure" or going to far away place. My theory is, always make taking pictures some form of an "adventure" or otherwise it's not really worth it. Even it's going to the same place over and over, do it differently, and go into "adventure mode".
Night Photography
Astrophotography: The use of photography in astronomy; the photographing of celestial objects and phenomena.