Have you tried charcoal drawing yet? Some people love it, some hate it - the latter often because its a bit messy... well a lot messy, but that's part of the fun. Don't let it put you off. I like charcoal, in part, for the amazing depth of black that it gives. Charcoal particles have a rough, irregular surface resulting in a matte, velvety surface. You can easily see the difference when you use it next to graphite - the round, smooth surface of graphite particles reflects a lot of light, giving it that characteristic sheen. Charcoal allows you to develop rich, atmospheric drawings with considerable depth. Working the full surface of the drawing and with a properly lit subject, you can get an excellent sense of form and volume.
Charcoal is also a wonderful medium for line drawing. Using the corner of a charcoal stick allows you great control over lineweight, so that you can create sensitive, expressive lines. Charcoal is also a surprisingly inexpensive medium. If you haven't tried it yet, give it a go.
Favorite Drawing Charcoals
Select a Paper for Charcoal and Pastel
Charcoal and Graphite Drawings

Image: The Skull Charcoal Study © Alberoni