mines been rattling on high fan since new. The dealer tried "tightening" it etc. They gave up and said it was a factory design flaw. I complained to Toyota and they were no help. After a few months, I complained at the dealer again (with a different service writer) and he order and installed new vents. So far so good.
I am replacing interior parts one-by-one in this car. a/c vents, console parts, rear speakers, sun visor, the list goes on. I hope to eventually get rid of all the buzzes, rattles, squeeks, etc. Hopefully, before the warranty runs out.

If Toyota doesn't step up to the plate on these quality control issues, I'm heading back to Honda. A shame really, since the Hybrid components work so well.