Create your own unique scene in Unity using assets you acquire (free or paid) and export it for standalone Mac. Make sure it includes at least the following:

• A terrain with one or more textures applied, and some mountains.
• Find at least 3 free objects in the Unity Asset Store (Windows > Asset Store) and place them in the scene. You can also find free 3D assets at http://www.turbosquid.com/, CGTrader, and free textures at CGTextures.
• Assign a skybox, either the one in the class demo, or if you're feeling adventurous a skybox you find in the Unity asset store or elsewhere online.
• Add at least one sound to an object.
• Put a First Person Controller into the scene. You will find one in the Project pane I had you download from the NHStorm server under Standard Assets > Contollers. Find a folder in there called Prefabs and you will eventually see a prefab for the first person view. Drag that into your scene and position it, and then push the Play button and you will be able to move through your scene.
• The last step is exporting. Go to File > Build Settings and choose PC and Mac Standalone. Choose Mac OSX in the Target Platform pulldown, then Build. Choose the desktop for the location, and when it finishes building a new icon for your scene will appear on the desktop. You can double click that to run it independent of Unity.