Graphite. the final frontier:-)
The secret about pencils is this:
Different pencils have different characteristics and unique qualities. Instead of looking for the perfect pencil look for the right pencil for the specific task.
Here are some examples.
Task: I want a dark fat line to show the solidity of this large figure.
Pencil Response: 6B to 9B graphite block or woodless pencil.
Why? Because this soft graphite will make mostly fat lines because the softness makes the point go away quickly.
Task: I want a range of mid-tones blending across the elegant cheekbone of this model.
Pencil response: Use the side of the lead of a 3B-6B pencil to shade in the form form light to dark. Layer the pencil shading until you have approximate values you want and them blend them with a blending stomp.
Task: I want very precise lines to show the definition of the toe bones.
Pencil response: Use the point of a relatively hard pencil but for drawing for the web usually going harder than HB makes it difficult to see so the more contrast the better.
Pencil adventure. Go to the art supply store with your sketchbook and try out the pencils by making sample lines and marks on your pages. Take notes on what kinds of pencils make what kinds of marks. Usually art supplies store have little pads of paper by the drawing supplies, but put your marks in your own sketchbook for future reference.
What you are looking for is not the perfect pencil, but the perfect marks. Let us know about your adventure.
Don't forget white marks on dark paper.