Bill Lavoy (Prima Games): Call of Duty: Ghosts has a lot of kill streaks for players to choose from. The Guard Dog, also known as Riley from the single player campaign, is not only one of the most heartwarming characters, he's also one of the deadliest options. He will follow you around, keeping you safe from opposing players trying to sneak up behind you. He'll even get revenge if you're killed. When you re-spawn into the game, Riley will make his way across the map -- killing anyone in his path -- and return to your side.