The Johnnyguard Achievement
Prevent Johnny Tag from taking damage on the Magarac Bridge.
You will have to take out Jeeps, Snipers, and Helicopters without Johnny taking any damage. When you are destroying the helicopters, don't wait for a lock on instead fire it and guide the rocket to the helicopter. If you see Johnny take any damage you can restart from checkpoint otherwise if you finish the mission you must restart from the first mission.