Yesterday was the first time that I needed to use the F4 function key on my PowerBook for something else than lowering the volume. The problem is that by default, the F4 key does just that, it lowers the volume, so what to do?
In my case, I wanted to toggle between absolute and relative cell references in NeoOffice Calc, you know, cycling through the A1, $A$1, A$1, and $A1 options. My first idea was to define a new keyboard shortcut via System Preferences -> Keyboard & Mouse -> Keyboard Shortcuts, but that requires you to know the precise menu command from your application. It turns out that there is none in NeoOffice.
Next I had the idea to try to customize to keyboard shortcut from within NeoOffice, and while it is possible to redefine keyboard shortcuts via Tools -> Customize -> Keyboard, it does not seem to be possible to change the default from SHIFT+F4 to something else.
I finally found the solution in OS X’s System Preferences -> Keyboard & Mouse -> Keyboard pref pane. There is a checkbox
Use the F1-F12 keys to control software features. When this option is selected, press the Fn key to use the F1-F12 keys to control hardware features.
This works as well as it sounds. My last only concern was that it might be inconvenient to press Fn every time I wanted to use ExposÃ© or Dashboard since I use them much more frequently than the volume and brightness controls. Fortunately, the F9-F12 keys do not control any hardware features. Furthermore, it is not necessary to hit the Fn key when using them, so all is well.