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 used a Platinum Preppy fountain pen for this. I like how it makes me kinda happy looking at it haha. I made this into digital form ( made it a little happier with more smiley faces) and put it on my Redbubble and TeePublic.