One of the nice things about having a lazy Saturday at home is that something random on TV will spark inspiration. This weekend, it was the History Channel (which, every once in a while, remembers that their focus is history), and 101 Objects that Changed the World. The list is basically a bunch of tangible items that represent some major change in the world, or some major event in history. It includes things like the hard hat (which allowed major buildings and bridges to be built safely), the cannon ball shot at Fort Sumter (beginning of the US Civil War - the list is a bit US-centric, shockingly enough), and the Coca-Cola contour bottle (first major company to use uniform packaging).
It made me wonder what objects would be considered "essential" in a world that I'm currently building. There's the big important thing, in this case a golden rope that magically binds the different territories of the land together, but that's not something that the average person would encounter on a daily basis. The clockwork servants, however, are things that are so common that they fade into the background.
To me, an important object for a world is something that helps differentiate the world you're creating from the real world. It can also help you figure out how your setting got to where it is when your story is taking place. A story is a snapshot of time in a greater timeline, and it's helpful to remember that there's a history to the world you're writing in that influences the way your story takes place.