There have been previous versions of this question that were closed since "there is no reason to create a one-off actual thumb drive", however, I have a very specific idea for a USB flash drive in mind.
I am getting married next year and I'm thinking of the save-the-dates in the form of a USB dongle. This would actually be a PCB with a USB plug that, when plugged in, flashes a few LEDs on the PCB and contains a multimedia file announcing the wedding date.
I figure I'll use a small microcontroller to control the LEDs. That part is easy and well within my skillset. I probably need a NAND chip and a controller for the flash drive part. Has anyone ever done this before? Any guidance would be appreciated, even just suggesting ICs to use, or a schematic to read over.