Anastasia's Brow Wiz is a brow pencil on one end and a Spooley brush on the other for gentle coloring and blending. You can find it at: http://www.sephora.com/browse/product.jhtml;jsessi
Anastasia is the "guru" of eyebrow products and I personally love her Brow Powder Duo. If you're interested in taking a look at it you can find it at: http://www.sephora.com/browse/product.jhtml;jsessi
I hope this helps you.
The best way I have found to fill in or darken eyebrows is not with a pencil; it's with a powder. One I really like is from Bare Esentuals. They have an awesome brow powder...you can top it off with either a brow wax or gel.