A little-known trick will allow you to run your Mac's screensaver as a desktop background. You can use this to have an animated desktop, display useful information, or just for fun. It could be useful in situations where you have your Mac just playing music in a shared space and want something more interesting being shown than just a static image.
If you'd rather not take your hands off the keyboard to access the Mac menu bar, you can execute any menu command using a keyboard shortcut. You can then use the arrow keys to navigate through the menu items and Return to select one. You can do something similar with the Dock as well.
If you want to go beyond System Preferences and change other settings on your Mac, you can do so with the Terminal window. But TinkerTool makes it even easier by giving you a list of potential settings and a user interface to make the changes without typing.