Two great Mind Mapping pens for ink work: Faber-Castell PITT Artist Pens and Staedtler Pigment Liner
These pens have Waterproof and lightfast ink; perfect for black line work
They come in both fine line and thicker line:
The Faber-Castell F and Staedtler 0.2 are versatile sizes, ideal for drawing and lettering
Personally, I like to use black ink then add colour these pens are great for that.