An oldie but a goodie.

Charcoal

So I remember there's something special about this piece.  I don't remember what the technique was called, but what I had to do was color the entire paper black, and then define and shade the skull with an eraser--basically, the drawing process was inverted. 

Hahaha, I also remember I got a B on this because I didn't emphasize the way the light hit the skull enough, which was the entire point of the activity.