Decapitation

If Lord of the Rings has taught us anything, it's that nothing is cooler than lopping of an orc's head. I'm an animator, and I really don't know too much about rigging. But I would like to animate a sweet decapitation. So how hard would it be to modify an existing rig (like the ones here on CC) to be able to have the head come off. I think the easiest way would be to have a normal rig, and then a headless rig with a seperate rig, and then just switch them out (turn visibility off/on). I don't care too much about blood, etc, just the animation. Any suggestions?

Thats a good way if you want to do minimal amount of work.