Once in a while, when I melee an enemy soldier, Drake pulls off a piece of kung-fu action and kills the enemy while whisking away his gun (for example, in one, Drake kicks a shotgun out of an opponent's hands and then grabs it as it falls down). In another, Drake pulls the pin from a grenade that an opponent is holding and then kicks them away, so that the grenade kills them a few seconds later.
Frankly, I think all these animations are pretty cool to watch, and I'd like them to happen all the time. Unfortunately, I'm not sure what conditions are required to get them to trigger.
Are kung-fu disarms random in Uncharted 3, or can I force them to occur?