Definitely my most favorite subject to shoot has to be fauna, which includes anything from caterpillars, bees, butterflies, chipmunks, deer, or bears.  They are fascinating to watch, and present their own challenges when trying to capture them.  One must learn to be patient, and spend as much time as possible watching, and learning the habits of their subject.  The more you become familiar with your subject, the more you are likely to anticipate what they will do next, and when to snap the picture. But the time, patience, and effort always pays off in the end.