I recommend the Clio Sharp So Simple Waterproof Simple Liner.

I highly recommend the Clio Sharp So Simple Waterproof Simple Liner!! It is a product I have been using consistently. Since it is waterproof, it smudges less, and because it is a pencil type, it is very easy to draw with. Also, the color is natural, so you can draw without looking too heavy. I strongly recommend this product to anyone who uses pencil liners.