Active ragdolls?

Hey there, I am stuck. I would like to add physics to my player animations like in GTA, gangbeasts, overgrowth, totally accurate battle simulator and max Payne. I have no idea how to do this. I have the default 3rd person controller and want the animations affected by physics so for example when I play a punch animation my fist actually applies physical force to other active ragdolls/rigid body objects. basically my player mixing ragdolls with animations. Thanks!