Call of Duty: World at War is considered the hardest game in the series, with intense enemy presence, constant fire, and challenging missions that make it the ultimate experience in terms of difficulty.

1. Black Ops II. Call of Duty: Black Ops II took everything that Black Ops did right with the Zombies mode and perfected it even more. No one thought this would have even been possible, but Black Ops II created the perfect and best Call of Duty Zombies mode of all time.

Other variations included the terni lapilli (three pebbles at a time) from the Roman Empire, three men's morris from various parts of Asia, and Picaria from Native Americans. The name tic-tac-toe  came about when the British name of noughts (zero) and crosses  was first printed in a scholarly journal in 1858.

No one knows the Roman name for it, but scholars call it ROTA, Latin for wheel.  ROTA boards were painted, scratched or scribbled everywhere that Romans went. It probably kept a lot of bored Roman soldiers busy. Scholars guess that ROTA is a three-in-a-row game like tic-tac-toe.