How To Unlock: Kill 10 enemies with throwing knives.
For this trophy you have to get a total of 10 kills with the throwing knives. Equip them by pressing (UP). Throwing knives will normally cause instant death to enemies and can be picked up again from the enemy's corpse. The kills will accumulate even if you die before reaching a checkpoint. There are plenty of opportunities to get kills this way, so this shouldn't be a problem.