There's also radians/sec, which comes up in network analysis. Radians correspond directly with things in the real world, like analog filters (cutoff frequency omega of a single-pole filter in rad/s=1/RC). Radians/sec are used because the math is a lot simpler. Switching to Hz puts pi into the equations, and switching to three-legged pi (thri?) would put 1/2 in the equations.
