Contest: Why Is This Desktop Empty?

I just had a situation where I was facing an empty desktop with no way to logoff, start a program or do anything else. The only thing left to do was to log the session off from an admin session. This got me thinking: how many ways are there to create such a situation? I am writing down all the ways I know of and ask everybody to contribute. Can you come up with a way to end up with a completely empty desktop I and no one else thought of before?
Citrix/Terminal Services/Remote Desktop Services
