How can I rename how my Arduino shows up on the computer?
This string is contained in the FT232 USB to UART interface chip and the manufacturer has released the FT_PROG tool to reprogram it. But do take note of the warning on their website: "PLEASE NOTE - The use of some of these utilities by an end user may result in a device being rendered useless". Another word of warning is to ensure there is only one device connected with an FTDI-chip.

Here is a screenshot of the MProg tool: