Just turning the screen upside down is a classic and works very fast If you know the shortcut, but my favorite was always:

1. taking a screenshot of the desktop
2. flipping that screenshot upside down
3. disabling desktop symbols
4. setting the taskbar to auto hide
5. using the flipped screenshot as desktop background
6. and finally flipping the screen.

Results in a normal looking desktop with an upside down cursor that behaves weirdly