This is the quickest way to take off a guy's head in practice I've found.

Set both players to all hold, then, before anything happens:

1. Set your guy's abs to extend, and both shoulders to contract. Also, click both hands to make them grip
2. Press space twice
3. Switch the abs to contract and the shoulders to extend, AND contract both pecs
4. Press space three times

Victory!

edit: pictures

End of step 2:



Step 4:


Success!


I decided to throw his head.


Bonus points for distance