Although it proves itself to be more polarising with each passing year, Call of Duty is hands-down one of the highest-grossing and dependable franchises out there. Regardless of how much each subsequent development team have taken the base formula in all sorts of directions (there are three teams working on COD in 2015), you can't deny that when you get hands-on with each annual instalment, it feels immediately familiar, tactile and above-all enjoyable. 2014 saw newcomers Sledgehammer Studios leapfrog off the Black Ops II mentality of taking things to a more futuristic plane, doubling down on the possibilities therein to give us ability-extending EXO suits, boost capabilities and essentially super strength. It ended up dividing the fanbase chatter online, but for the most part was a resounding success both commercially and critically - leading to this year's Black Ops III continuing in very much a similar vein. However, the teams that put together such a well-regarded and perfectly-playable franchise aren't just trotting out the same level layouts or environments every year. Instead, everything has to be consistently built upon and refined, leading to all sorts of juicy secrets and little-known easter eggs tucked away every time.