"Pilot V Razor Point (Extra Fine)" is the weapon of choice. I'll be switching back to an old school "Crow Quill and Speedball Black india" when I feel I've done enough of this farting around... and want to move on to actually "finished pieces".
I use "Pilot V Razor Point" because they are good pens and you can draw for days without them running out. However it's not the pen that makes the art.
I've thought about putting a few of these on Zazzle.com as prints. Maybe after I've drawn something worth a crap. These are just "exploratory doodling".