Hotkey software that lets me set up my own Fn keys (which override...)

I am looking for some software (don't mind paying a few $) that lets me set up Function keys or special keys that will override even the current program I am working in.

So, (this is just an example) - - the WinKey+S is "Save" in an application I am running. I want that key to do something else, like Open a Windows Explorer window...

AutoHotKey.