There is an important class of systems that are often used.  Those systems are systems with poles at the origin (s = 0).  Integrators are often used to drive SSE (step input) to zero when SSE is important, and adding an integrator adds a pole at s = 0.

        Since these systems are important, it is important to understand their Nyquist plots.  To get you thinking about the Nyquist plots for these systems, sketch the Nyquist plot for systems with these transfer function.