8. Day Of Defeat (2003)
Nowadays there has been an influx of multiplayer-only WWII indie shooters such as the popular Red Orchestra series, Day of Infamy, Days of War, War of Rights, Verdun and the now-hyped Battalion 1944.
However, the game that inspired all of these shooters was Day of Defeat, which first appeared in 2000 and was officially released in 2003.
Day of Defeat had an uninteresting origin as a WWII conversion of the classic game Half-Life, but to the surprise of many, the Western European theatre combined with tactical multiplayer gameplay were loved by fans. Similar to Counter-Strike, the game used scenarios that encouraged team-based tactics rather than individualistic combat. It was also chock-full of realism such as recoil and controlled accuracy when firing guns, and early versions had friendly fire and bleeding out when hit in a vital body part.
Day of Defeat was special in terms of lasting influence since it was a free to download modification by independent developers, which became an actual game when publishers saw how popular it was. Its success inspired many independent developers to modify their own WWII conversion or release their own multiplayer-based WWII shooters.