SFunKey

SFunKey is an easy-to-use but powerful program that enables users to remap their functional keys. It comes in handy for setting media controls to keyboards that do not have built-in media buttons, for example.
The installation procedure is quick and does not require special attention from the user. Once it is done, you can check out the user-friendly interface, represented by a regular window divided into three separate and well-organized panels. The main application window has to be brought up from a system tray icon.
A list of all twelve functional keys along with the Escape button is shown in the secondary pane. All you have to do is select a key and pick a corresponding action between power management options (e.g. sleep, restart, lock, shutdown), LCD brightness increase and decrease, volume adjustment (increase, decrease, mute), media playback (e.g. play, pause, previous or next track), and others.
In addition, you can disable running applications, change the interface theme and language, set SFunKey to automatically run at system startup and to remember the window position, specify a fade out delay and popup speed, adjust the transparency levels, and so on.
SFunKey has minimal impact on system performance, running on a low amount of CPU and RAM. It is very responsive to commands and works well, without causing the OS to hang, crash or pop up error dialogs. We have not come across any issues in our tests.
To sum it up, SFunKey is a reliable piece of software for assigning media, power management and other types of control to your functional keys in a user-friendly environment that does not require special experience.