Making a Mark

With my efforts to improve my illustration skills I have been thinking more about mark making tools. My weapon of chose is usually the nearest pen or sharpie lying around. They are good enough tools, but do not allow for much variation in line width or my illustration characteristics. Different tools that have some interesting qualities to add to my pen drawings:

1. Watercolor: one of the easiest marking tools to add, since I have a watercolor set from my grandmother and some brushes that I can begin to dabble with this fluid form.
   
2. India Ink: this thick black ink was a great tool for my serigraphy prints in school, because its light-fast qualities. I still have some lying around. Similar to watercolors is that this ink can be very fluid, but you can use it with a calligraphy pen for more control.
   
3. Potato Printing: I have always wanted to try this technique. I have all the tools I need for this, but have always been hesitant to waste these delicious spuds on something other than food. But the texture these prints can supply would be worth the risk. Definitely it is on my must try-list.
   

Do you have any favorite techniques you like to use?
Photo from Oh Happy Day!