Specifically, these are different weapons inspired by Halo, which were added to Destiny 2 as part of Bungie's 30th Anniversary Celebration Event. While they are not exact replicas of their counterparts that we have come to recognize in Halo, the event includes a number of free weapons that include guns based on Halo weapons such as: Magnum, Battle Rifle and Energy Sword.
The celebratory event is launched together with the Destiny 2 30th Anniversary Pack, which costs € 24.99 and features, in addition to weapons, also a new dungeon plus content based on previous games developed by Bungie including Marathon and Myth. New cosmetic items also include the Myth Claymore sword, legendary weapons from the first Destiny, the exotic Gjallarswift Sparrow, Marathon-themed armor, and the Gjallarhorn rocket launcher.
Bungie is one of the development studios. which made the history of the video game, acquired by Microsoft in 2000 before the release of the legendary first chapter of Halo, and separated from Xbox in 2007 after opening a new era of the company with the Destiny saga.
You can purchase your copy of Destiny 2 on Amazon at this address.