You can say that the Call of Duty series’ was destined to stir up controversy. Modern Warfare 2 has an optional mission called 'No Russians' where you play as CIA op, Joseph Allen, working undercover with a Russian terrorist group that is carrying out an airport massacre. You can opt out of shooting any civilians during the mission. In fact, developers gave you the option to skip this level entirely without penalty as well as the option to skip ahead of this level at any point. Attacking civilians has been a part of several games before Modern Warfare 2, though that has been optional mischief, compared to in MW2 where it's part of the mission and rather gruesome. The MW2 Russian version scrapped this level entirely, and the Japan and Germany versions give you "game over" if you kill any civilians.