I am addicted to pens, markers, lineart and fingerpicking on my Taylor guitar. I carry at least 20, if not 30 pens/markers with me at any time. I am not the only one - my brother and my daughter are pen freaks, too. I love walking into Curry's or Staples and walking down the pen and marker aisle. I gave each of my daughters a whole new set of Sharpie's for Christmas - and Easter. There is nothing like a new marker - except new great paper to draw on.
I like to draw on paper that is slightly rough - like oatmeal paper, manilla paper, cardboard, rocks. I use a .5mm black marker most of the time. How can I be so addicted to different pens of the same size and colour? I don't know, but I am. If not that, I use a calligraphy pen and India Ink. Sometimes I use India Ink in different colours - oooh - so daring, eh?
Once or twice I watercoloured my drawing. It was nice. I like watercolour painting, but I need more time to experiment with it. My daughter bought me a bamboo easel for my birthday/Christmas/Mother's Day. She likes to save it all up and come back with a bang.
I like doing these because they are a luxury to me - I immerse myself and don't think about time, or chores, or the gym, or problems. I escape and doodle.
The only think I like more than lineart doodling is fingerpicking, writing songs and singing. I must be OCD. But, hey - everyone has their foibles.