9. Various Rooms - Hollow Knight
When you design a game that relies heavily on making mapping and moving areas as relatively straightforward as possible, you're more or less set to create areas that you later have to cut along the way.
This is the exact reason why anyone scouring through Hollow Knight's game files may notice that many of the places you can find there don't actually exist in the game proper.
These were so abundant that a helpful modder actually created a way for players to access all of these rooms, only for this method of exploration to be rendered impossible with Hollow Knight's Hidden Dreams update, which removed these areas from its files.
And it's unclear why, as there was nothing but intrigue around these unused areas. They're absolutely beautiful, in the uniquely understated way that much of Hollow Knight's set pieces are, and raise all sorts of questions when you see them.
For example, why is one of the rooms made seemingly entirely out of yarn or wool? Why is there a room that is filled with statues of moth people? None of it is entirely clear - but all of it is decidedly wonderful to speculate about.