Slingshotting
When a vehicle is unavailable, using the grappling hook to transport yourself quickly is the best option. Target any object other than the ground and grapple it, then reel toward it. Press A to pop the parachute, using the momentum of the reel. To get around faster, release the chute and grapple the ground while falling.
Towing
The grapple can be used to hitch two objects together by grappling, holding down the button and releasing on a second object. These objects can be vehicles, explosive barrels, people as well as any solid surfaces. This can be used in creative ways, such as attaching moving vehicles to stationary objects or tripping two opponents by connecting them to each other.
Combat
Grappling can be used to throw opponents off high places, juggle them with gunfire or suspend them from objects. This is especially useful against powerful opponents or dealing with multiple opponents. Due to this incredible amount of empowerment, the game is balanced in such a way that makes opponents deadly accurate, so mastering the grapple during combat is important.
Hijacking
During the vehicle chase sections, your agent can actually leap onto the side or hood of the vehicle while it's moving, in order to fight enemies. For particularly tough enemies, it's best to use the grappling hook to hijack their vehicles so you can kill them one by one. For many flying vehicles, grappling is the only way to hijack them, as helicopters will hover close just to give you an opportunity to do so.