I'm a big fan of Hipshot O Rings. Simplicity of a smooth metal knob with the grippiness provided by the rubber o rings. Look cool in my humble.
With regard to knurled knobs, I think the problem with them for me is that there are so many cheap looking knock off examples of them that I have grown to generally dislike them.
I absolutely hate chicken head knobs on basses though. What is that about?