For your first assignment you get to choose almost any medium in the class to work with! If you can't find something ask if it's available. The goal of this assignment is to show what you like to do, and what your favorite materials are to work with.
The only catch is that this assignment is due by the end of next class, so you don't have a lot of time! Make sure you choose something that can be completed in a couple of hours.
If you're not sure what you want to do talk with the teacher or look through the art books by the windows.