While the Nikko G and Zebra G nibs are often promoted as good nibs for beginners to pointed pen (with good reason), I have always found them to be good all round nibs for advanced practitioners as well.
While they would probably not suit very small x-heights, I have found that for heights of 4mm and above they are pretty good performers.
They are capable of good shades, smooth lines and very fine hairlines if the ink and paper combination works well together.
This quick piece was done on Canson marker paper with a Nikko G and walnut ink in an attempt to illustrate what it can do. The x-height is 6mm.
I hope it helps some people.