I also like using just black ink. Lately, I've been using this Platinum Preppy extra fine for my doodling. I like how different kinds of pens and tools can sometimes give different art.
I tweeted "Reply with a photo to this for me to draw on for @doodlers" the other day. I received a great photo from my dear friend Ashley. She was a friend in college. Her son's name is Pace. So cute.