Love it or hate it, the Call of Duty series is still one of the biggest franchises in the world of video games. Particularly since the release of Call of Duty 4: Modern Warfare in 2007, the series has become incredibly popular, thanks to its addictive blend of explosive campaigns and accessible multiplayer. In recent years, the Call of Duty series has been at the brunt of a number of criticisms. Most notably, many have accused the games of not doing enough to warrant yearly releases, with each successive entry only offering minor differences from the last. Thankfully, this year's Call of Duty: Advanced Warfare has made a bold attempt to buck this trend, by introducing a futuristic setting and featuring greater freedom in movement. There have still been issues with multiplayer connectivity and an uninspired single-player campaign, but most agree that Advanced Warfare is a step in the right direction. This list takes a look at ten of the best secrets and easter eggs that can be found throughout the Call of Duty series. From fun pop culture references to hidden unlockables that require strong teamwork to uncover, each of these entries gives good reason to revisit the series.
