I had a rattle coming from somewhere near the rear hatch. I pulled off the license plate and the rattle went away! I guess it rattles because the plate is slightly elevated with the rubber stops on the bottom/top. So I put a little weather stripping on the back of the license plate (the kind that you use to seal a window) and the noise is gone! Seems to have worked but i'l only know for sure after a week or so of driving. I'm not 100% convinced this was the solution because the rattles were intermittent, but if it was the license plate, then it should always sound. Guess I'll find out!