I have a clone of a Mega 2560, and the Chinese manufacture apparently had a broken shift key. To my annoyance, whenever I connect it to my computer it reads,
arduino compatible mega 2560. With my extreme annoyance with slightly misspelled or incorrectly capitalised English, it has been very distracting to me.
However, the reason that I'm asking this question is for more than how to rename it to be capitalised. Think of how many projects could be simplified by this! Or for many Arduinos, you can label they physically and then rename them
Arduino #1, etc. so you can tell which port it is on using device manager. If you designed a product with Arduino, then you can even rename it to your product name.
I would imagine that there would be an easy way to do this by reburning the firmware to the [Insert USB chip model #### here]. I've seen it done for keyboards on the Uno, so I would imagine that you could modify it somehow.