Gunning Trophy in Prototype
Destroy 20 Helicopters in a single Helicopter flight.
How to unlock GunningThis trophy is no longer a pain thanks to PS3T.org user HUYI and YouTube user Thegamingguru65. Simply put, once you have the ability to fly helicopters from the mission "Biological Imperative", hijack a helicopter, fly to the location where you start the Friendly Fire kill event, and destroy the helicopter sitting there 20 times. Here's a video showing you how to make the helicopter respawn after destroying it, and to prove that unlocking this trophy really is that easy:
Alternatively, you can start either the Friendly Fire or Death From Above kill events. These task you with destroying enemy helicopters that are out to get you. You will get infinite homing missiles and if they blow up your helicopter before you get twenty of them, it will end the event which will prompt the game to ask you if you'd like to try again, which will give you another chance at the trophy with no extra effort on your part.