For as long as I've been doodling my earlier works I've been using a pencil. The versatility and depth offered by such an inexpensive material was invaluable to my work, while it also features as the base material for all of my other work.
Pastel was a fairly slow development and even now only has a few select pieces to show, but I am constantly looking for new- and unique- things to use pastel for.
Likewise coloured pencil was once a shy material and would only show every so often, but as of 2012, and earlier in 2011, it has become a lot more bold. Showing itself as a great standalone material.