Just yesterday I was going mad with my new bike and it's click/rub noise. I'd just put fenders and a rack on. Plus it has disc brakes, all possible noise creators.

Nope

It was the plastic disk ("Dork Disk") on the rear cassette that wasn't on firmly. It was clicking and rubbing. It only took way, way too long to find it. It's now history. But I'm still a dork, I guess.