There are a number of different types of strokes used in pen & ink drawing but I think the most difficult is stippling.
Like most of the other strokes, stippling can be used for many subjects but it is probably most suited to delicate items. However, I find that I get carried away and often end up with a section where the dots are too dense. That means I have to go back and increase the dots elsewhere to balance the composition. Stippling is also very time consuming and, while I like the effect, I usually want to work at a faster rate.