This winter I've noticed that my rear deck (that consists of the speaker grills and brake light) gives a real annoying vibration at certain revs and when hitting bumps on the road. The only thing that slows it down is to shove a rag right between the rear brake light and rear window. This isn't a safety issue too much as I have an optional rear spoiler on mine that has a brake light as well.
I thought at first it was just the cold weather, but still does it when above freezing. I did check my speakers and amp and everthing else under the trunk seems tight.
