The pi is a complex piece of hardware. Each pi is somewhat unique.
Each RPi is, for practical purposes, unique by virtue of its hardware encoded serial number.
But that's all. Apart from that every RPi (of a given model number or type) is exactly the same as every other similar RPi that comes off the production line.
Every use that is made of an RPi is unique? That might be getting closer to the truth. And isn't that the conundrum with trying to write 'use case' scenarios - each one is different and does not exactly match the searcher's requirements.
That's what makes the Raspberry Pi Mission Statement so powerful:
Our mission is to put the power of computing and digital making into the hands of people all over the world. We do this so that more people are able to harness the power of computing and digital technologies for work, to solve problems that matter to them, and to express themselves creatively.
Several use-cases a week get written up on the Raspberry Pi Foundation blog - https://www.raspberrypi.org/blog/
There is an archive that goes back to 2011.