Rated 5 out of 5 stars
I use the Firefox offshoot, Waterfox. Waterfox uses a legacy edition of the NoiaScrollbars, but they still look fantastic!
The customization of the scrollbars is made easy buy an intuitive user interface configuration screen.
It's nice to be able to actually see the scrollbars by adjusting their colors to exactly what you want to see, or you can hide them completely if you so choose. NoiaScrollbars makes those very easy to do.