The main brush I use for sketching and lining! It is meant to recreate how I use a pencil, and has a high tilt/pressure dropoff. I also use it for paintings and final touches at times. It is a smooth line.
Experiment with tilting the pen and various levels of presure, for the brush will change according to that! Feel free to mess with the opacity or anything else you'd like :) You can tilt the brush to the side and be able to quickly shade sketches with it.
Check out my Instagram and Twitter to see more examples of my brush in action: @Emnide
These two drawings used this brush for lining and painting: