Four new multiplayer maps: Core, Urban, Sideshow, Drift.
Exo Zombies mode: This co-op mode sees player taking on the role of four Atlas Corporation employees played by celebrities John Malkovich, Bill Paxton, Rose McGowan, and John Bernthal as they fight against a "new breed" of zombies.
New weapons: the AE4 directed energy assault rifle and custom variant, the AE4 Widowmaker.
Havoc is the first of four planned expansions for Advanced Warfare. The other three are called Ascendance, Supremacy, and Reckoning. Activision has not yet announced details on these expansions, though you can be pretty sure they will add more maps, weapons, and zombies content.