Created By: Unknown Troper on October 11, 2007
The bad guy has the good guy down on the ground helpless. He raises his weapon to get ready to kill him. He raises the weapon to bring it down on the good guy -- but then another good guy sneaks up from behind and kills the bad guy before he can get off the killing blow. (Of course the name also comes from Dungeons and Dragons and it is analogous with "Talking is a free action", but there might be a more concise name for this.)
Hello, Unknown Troper. You'll need to get known to lend a hand here.