The Utility shader has a super-fast ndoteye shading mode. This shading mode doesn’t trace any rays: it simply shades based on the angle between camera (eye vector) and the surface normal (ndoteye = dot product of the Normal and Eye vectors).
Here’s an example of the Utility shader. The middle mesh has the ndoteye shade mode (the left mesh has plastic, and right ambocc).
Note that with ndoteye you get just black in the glossy reflection. That’s because in ndoteye shade mode, the Utility shader handles camera rays only. No secondary rays like glossy or refraction.