Not sure what you are trying to say here, but non-Newtonian (non linear shear stress vs viscosity) fluids are common and studied.

Ketchup is non-Newtonian (shear thinning) as is corn starch suspension (shear thickening).

Non-Newtonian liquids aren't rare. In fact, if we consider pure water to be a Newtonian fluid just about every fluid in nature is non-Newtonian.