For a man wearing a suit the right jewelry can upgrade your look from smart to brilliant.
At the same time, ostentatious 'bling-bling' is distracting and unattractive; men's jewelry should always be subtle.
The watch passes the test by virtue of its functionality; cufflinks and tie clips earn provisional legitimacy on the same grounds.
The wedding band is respected for what it represents, and other rings may be subtle enough to work to a man's advantage in the right setting.
Piercings have featured prominently in so many counter-culture movements, from pirates to camp to punk rock, that they immediately arouse negative reactions from many.
If you are going to wear an eyebrow stud with a suit, the suit had better fit you like your own skin if you don't want to be remembered as 'the guy with the eyebrow ring.'