The Perfect Desktop: Tweaks Extension
Previously known as Tweak Tool, this extension is a graphical interface for advanced GNOME 3 settings. Yes, you could dive into several configuration files and edit things painfully in Vi, but why would you...?
GNOME Tweak tool enables you to edit a number of settings. While some of these changes, wallpaper changes, startup applications and the like are also available in the official System Settings tool, it's the Extensions tab that brings together all the Extensions settings in one place - see the screenshot.
It allows you to turn extensions on and off and also access the individual extension settings from on handy place.
It may not be revolutionary, sexy or rocket science, but boy is it useful.
You can install it via the software centre. Gnome 3 is, of course, a prerequisite. RC