This is a comparison between the NPR shader from the Mariko Project (which I used in my previous image) and a Shader published by Infinity10 on RDNA, he calls it a modified Sanne shader. Please take note, both shaders are very light dependent, the shader on the right can look more flat if a different light set is used.

But for a flat shader which even generates it's own lines, the second shader looks really good to me.

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

Avatar image of me done by Chidori.