This review systematically examines the use of additive manufacturing (AM), also known as 3D printing (3DP), in the various aspects of military applications such as firearms, armor and ballistic resistant structures, including those bioinspired. The main goal is to provide a comprehensive exploration of AM in armor and military applications. The materials and structures created using AM technologies are analyzed and reported. Dynamic loading, and impact via Charpy and Izod tests were also explored in the search, although not considered in the armor results to be tests typically conducted at low strain rates, far from a real ballistic solicitation. Recently, an increase in military applications has been found, particularly gun prototypes fabricated in diverse materials with AM. Although the innovation, low costs, and manufacturing are clear advantages of these devices via 3D printing, there are limitations, such as the worrying panorama of unclear regulations that prevent these weapons from eventually reaching ordinary citizens. Current perspectives, opportunities, and challenges are discussed.