Although I have a handful of university level studio art courses to my name, I graduated with a science degree, not an art degree, and on the whole I am self taught. Pencil was my first love, and it was the first medium I really excelled in. I was a dedicated pencil artist for years before I began to experiment with other mediums...but once I started, it was impossible to stop. My art is in a constant state of evolution and it's difficult to break it down into straightforward categories, as I often use a variety of mediums to finish my pieces, but these are the foundation of my work:
Graphite
Colored Pencil
Sounds like a good medium for a 5th grade art project, not a professional artist, but colored pencil has become one of my most well-loved and most versatile mediums, and, furthermore, it is the foundation of the pieces I consider to be my greatest work to date. I use both oil-based colored pencils and water-based colored pencils, often mixing them with other mediums and blending agents, but never with one another.
Watercolor and Watercolor Pencil
Watercolor Pencil
Watercolor pencil is a bit of a crossover category. It's colored pencil, of course, but I rarely use it without also using watercolor paints. Like watercolor paints, watercolor pencil is a fantastic medium for a more loose, relaxed, fun, quirky and abstract composition. I am only in the early stages of familiarizing myself with this medium, but I see in it a great potential for smaller, more impressionistic portraits.

Watercolor is my newest medium, and it is quickly proving to be versatile and a lot of fun. I use it as a standalone medium, but I also often mix it with watercolor pencil and/or ink, to create really interesting effects. Watercolor is a wonderful medium for more impressionistic pieces, in which I allow myself to "draw outside the lines," so to speak - or paint, as the case may be. Watercolor is somewhat unpredictable by nature, and I find it a wonderful medium for my impressionistic portraits, which are more loose and abstract, more about the personality and energy of the animal than about making sure each whisker is at exactly the right angle. It can also be a great option for those who want to commission an original work of art that is a little smaller and less expensive than my typical portraits.