Guardian Angel is an Activity in Saints Row: The Third, making its first appearance in the franchise.
Unlike the other Activities, Guardian Angel is only accessed during the storyline - in the Prologue for Pierce Washington, and in Kinzie Kensington's line of missions.
The premise of Guardian Angel is protection - you are using a McManus 2015 and an Annihilator RPG in one of two parts of the mission.
When you are on the move, you are using the Annihilator RPG to blast away anyone chasing Pierce/Kinzie (either Morningstar or the Deckers, based on which person you are protecting) as they drive along. You need good aim, and to take them down before they get close to your interests. You can easily cause damage to Pierce/Kinzie by yourself with careless shooting.
When you have stopped, you have to use the McManus 2015 to protect Pierce/Kinzie from afar. Look for enemies, zoom in and line 'em up. Eventually, you will complete the mission after you have protected them for long enough. All that is required is good aim and common sense. These coupled together will make Guardian Angel an easy Activity to complete.
