How do you use the ballistic knife?
I specifically want to know how to initiate the attack animation where you stab somebody with both knives simultaneously, but any other information is welcome too.
You can stab someone with both knives when you are in the process of reloading the ballistic knife.
To stab people with the ballistic knife, you just use the standard melee attack button. To shoot the blade, press fire.
Remember to pick up the blades you fire whenever you get the chance.