I've had my external flash for almost a couple years now. For the most part, I have just used it for studio work, and for shooting events (Weddings, dances, etc.).
Recently, I've been looking at all kinds of interesting and extremely creative flash photography. I am starting to fall in love with it. Like to the point where I might only take photos with my flash. There is something uniquely creative about having a portable and off-camera flash that you can put anywhere. One photographer who uses flash in a very creative (Yet somewhat dark manner) is Luca Pierro. http://www.flickr.com/photos/sottounponte/
Although the above shots are more dark and pessimistic than all of my other work, I still am drawn to it. I've talked before about duel nature, and how everyone has a good side and a dark side. Being a Christian, I won't delve much further into this sort of creepy photography, but I like the concept behind these images.