When writing a book, it's common to start at the beginning and then work out what happens from there. But why not start at the end?
Beginning with the ending may make a lot of sense if you're writing a crime thriller as it allows you to know who done it, where, when and how. Once you know that, then you can build in your false leads when you continue writing the story from the beginning.
It could also work in other fields, for instance, to pick a genre out of thin air, Science Fiction Comedy...oh yes, that's what I write. By deciding what the ending will be, I will know where I am aiming to get, who to get there and what they will do once they arrive.
It's not something that I plan on doing a lot, but it is an interesting approach that is worth experimenting with, especially if I get stuck at some point in my writing.