The worse it is for writing, the better for drawing! How did I manage to overlook the most common office tool all these years? I've always hated writing with ball point pens, and for over a decade I have not used one to write anything longer than a phone message. Now, I'm totally fascinated with them, thanks to Adina Bricklin, an artist who showed me some of her original Bic pen drawings. Her pieces had such a nice soft shading quality to them that I had to try out the tool for myself.
I've found the ball point pen to be the ideal pen-pencil hybrid. It can go really light and handle all shades like a pencil, but unlike a pencil, the marks don't smudge or smear under your hand. And no sharpening needed--I had lost interest in pencil drawing partly because I got tired of spending more time sharpening pencils than drawing. The only drawback with these pens is that you can't undo any mistakes. With a little fixative spray, you can remove the reddish/purplish shine in the dark areas.
The cheap 5 to 25 baht ones (0.15 to 0.75 US$) seem to work best for pencil-like drawing because you can get that "dry" effect for lighter shades. Expensive writing pens usually give cleaner, more solid lines. Different brands have varying smoothness and respond differently to hand pressure. Here are some of the pens I've been using: