[i]Call of Duty[/i] is a series of First Person Shooter games that used to take place in World War II, but now they expanded to the modern age, the Cold War, and the future as of now. They are mostly known for it's multiplayer, especially with the latter games containing killstreak rewards starting with [i]Call of Duty 4: Modern Warfare[/i], and regenerating health starting with [i]2[/i].