It is possible to push an app, document, or profile to a single device. This is done on the overview of a device under Managed Apps, Documents, and Managed Profiles shown in the screen shot below.
When navigating to one of these tabs, you will see a button to add a single app, document, or profile to the device shown in the screen shot below.
Clicking this button will open a list of available profiles, apps or documents, simple add what you want and it will be pushed to the device.
To remove these single apps, documents, or profiles, navigate to the scope and click Remove.