I only use pencil. It's the only thing that would ever work with how messy my sketches my art and I always smooth out the lines afterwards. I guess I almost always draw everything with the intent that it can be a final piece that I will ink and maybe color later. I used to sketch some with pen when I was in high school and I developed a technique to do some shading with it and vary line width like I do with pencil. I just can't stand not having pencils now though. Must have mechanical pencils on me at all times!!