Well - this is hard for me... I look at composition, not necessarily subject matter. Right now, I am shooting pictures of buildings around my city. The challenge here is that building aren't really that exciting nor are they very dynamic but sometimes, with the right angle and the right contrast, I can get a good shot. Black and white is also limiting because buildings tend to be low-contrast and all-grey.
I would love to try to do portraits because I feel that a good candid portrait can say so much if done right, especially in black and white. But my main problem is that I am still shy when it comes to taking pictures of people. I am still uncomfortable pointing a camera in someone's face who doesn't even know me.
So - since I haven't really answered the question - I guess I can say that I have no favorite subject. When a print stands out and grabs me it is because all three elements (the exposure, the subject and the composition) worked together.