Laptop and USB cord. I also like to keep my journal and pen close by for little breaks to reflect on the day
I always want a pen/pencil and a piece of paper right beside my computer. I don't know why but I need to have them. Even If my computer has this notepad and sticky note apps available. I still rely on writing down what I need to remember. or even if the apps are open, unconsciously I would reach out for my pen and paper to write something and put that paper in my pocket.
A computer and a phone is basically an essential part of a properly functioning office. You will be needing it to perform all the basic task like sending emails, documentations and editing and some other stuff. Printer/copier, printing paper and pens is also a very good addition to complete the task at hand.
I think you've pretty much mentioned the items that every office needs. I think that pen and paper are the most indispensable office supplies, along with the PC.