In gnome you can configure a lot of advanced stuff using gconf that are not available in GUI programs like gnome-control-center. For example, in default gnomes it is common that new application windows steal the focus of current window. In my case, I launch eclipse (that takes some time to show the window) and a console. While writing on the console, when the eclipse window appears it steals the focus to the console and this is very annoying.
There is no option in visual tools like gnome-control-center for configuring this, but using the gconftool command line program we can check the state of the configuration property that controls the "new windows focus", like this:
gconftool-2 --get /apps/metacity/general/focus_new_windows
or can change its value to "strict" that will prevent focus stealing:
gconftool-2 --set /apps/metacity/general/focus_new_windows --type string strict
More, using the application gconf-editor one can inspect all available properties and edit them. Note that "metacity" is just another gnome application, in this case the window manager (the program that administer windows). The new windows focus policy is a responsability of metacity.