In the beta and tutorial, one of the most hilarious things you can do is throw any melee weapon directly at an NPC's head, rendering them unconscious immediately. It's done by holding L2/LT, waiting for the reticule to 'snap' to their cranium and then tapping R2/RT. Doing so can get you out of a pinch if any distant person is becoming suspicious of your actions, too. However, if you pick up anything sharp - like say a screwdriver or knife for example - lobbing it their way will embed it straight in their skull, leaving behind a satisfying human desk-tidy. Better yet, seek out the fire axe in the Paris level. Throwing this thing sees 47 raise both his arms and fling it with great force towards an opponent like Ezio from Assassin's Creed II, the resulting blow knocking your target clean off their feet. I'm yet to find anything so satisfying as skewering a target with a flying fire axe, but I welcome you to try.
