The best place for people watching in Nagoya might be The Golden Clock in Nagoya station. It is a favoured meeting place and around every full hour (e.g. 18:00h) the area is positively teeming with people. It is remarkable how much calmer it gets at around the ten minute mark (e.g. 18:10h), when all the meeting up is concluded and people leave to go do whatever they were meeting up to do.
In the above picture, it looks uncharacteristically calm. The video below gives a better impression of what it is usually like to wait for someone at the Golden Clock. For us gaijin, it is fairly easy to find the person we are meeting, or rather it is easy for them to find us, since most gaijin are at least a head taller than most Japanese people. If you have blond hair to boot, like me, it makes you virtually impossible to miss. But how Japanese people manage to find anyone in the crowd around the Golden Clock is beyond me.
As I already mentioned, it is one of my favourite places for people watching. Have a look at this beautiful young lady in kimono.