My tech discovered that a flying v style guitar was missing the bridge ground. Naturally, this was not before I had it converted from righty to lefty and converted to a master tone/master volume configuration and the pickup switch moved. Apparently, the stock configuration was quiet and fine... but move a few things and it was just a noisy mess.
I took it back and the tech added a bridge ground for free. Only took about 20 minutes. Being nice goes a lot further than some alternatives