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.
"Chillin'" Black ink on a sketchbook 2016
"That parent life" Black ink on a sketchbook 2016
Black ink on sketchbook. 2016.
Another mandala. 005 Micron black ink and graphite On heavy card stock