What drives me nuts with CORS is there's no (easy) way to disable it in the browser for development purpose, e.g. when I want to run some scripts in a local HTML file to do some basic web scrapping.
I was interested to learn about 'no-cors' where you get a sparse response. Was hoping to use it to find out if a web page was being accessed from a client's internal network or not (by trying to get a page that only existed there and inspecting the response)
In the end I didn't get to find out if it worked or not due to boring reasons.
At least Chrome and Firefox don't block it. I've recently used something similar as an add-on until I did exactly what he said: manually setting a cors * header for that internal development server