Mildon Studios has released Cajon Fu, a free VST instrument percussion box for Windows with two modes: Normal Cajon and Kung Fu mode.
Kung Fu mode allows you to play special sound effects like punches and sword drawing depending on the velocity of the hit, or you can play it like a real percussion box in normal mode.
Each track has its own volume slider and mute buttons for easy exporting as audio files. A special 'ghost' key allows you to play alight triple tap that's perfect for fill-ins.