Originally Posted by Robert_Nash

This is the location for the rear fog light which is required in many locations in the world (Japan, Europe, Canada, etc) designed to alert drivers approaching a car from the rear in foggy/low visibility conditions.

As far as I know, rear fog lights such as this are not "illegal" in the U.S. but apparently, the requirements for the U.S. Vs other countries are not compatable with the location/height, etc of the light on the Z; so, Nissan just puts a dummy/non-functional assembly in the spot (rather than completely re-design the rear bumper cover which, of course, adds a good deal of cost).

There are several threads on this that you might want to check including this one...

F1 Style Rear Blinker

I recently completed the work required to make my rear fog functional but there are many possibilities for this using this area.