One Key for Mac

From Everyday Software:

Do you miss being able to actually use the function keys on your keyboard? Remember when you could launch applications & open files with them? If so, One Key is for you. One Key is a simple, integrated and elegant solution for using the function keys on your keyboard to launch applications or files with a simple key press. One Key is integrated into the system as an OS X preference pane to stay out of your way. No fancy setup is required to get it working, unlike other hot key apps, One Key is one step simple.