Fusion Rifle

Fusion rifles are a class of energy-based weapons featured in Destiny. Advancements in directed energy disbursement were gained through dissection of hostile alien technology gathered in the field. The first implementation of this new technology resulted in the creation of fusion rifles. One of the first working prototypes was deemed too unstable for mass production due to faulty radiation shielding. Modern fusion rifles use a pulsing emitter in order to keep heat buildup to a minimum. Consequently, fusion rifles actually fire seven distinct beams in very quick succession. Because of this, users have had luck sweeping the weapon across multiple targets, eliminating all of them with a single fire event.

Fusion rifles are intended for medium range combat, significantly outpacing a standard shotgun, and must be charged up to fire. The charge speed varies per weapon, but in general it makes the weapon significantly slower to fire than a shotgun. If the user is adept, they can bypass this delay by pre-charging the weapon before acquiring line of sight to his target. In terms of range, the fusion rifle is intended for medium range combat, significantly outpacing a standard shotgun. While it was not built to handle long range combat, users that can tame its recoil and have a little luck on their side may find themselves picking off targets outside the approved range.

Source: Destinypedia

PvE: Fusion rifles can be deadly and can be used against a crowd of enemies. The individual successive beams it fires can easily take out shields of targets, especially at close or medium range. Each beam's damage is identical, making it effective in taking out more resilient targets.

PvP Using a Fusion Rifle in PvP requires advance planning, simply because of the delay caused by the charge time. One popular method is pre-charging the weapon and anticipating where the player or target will move. If one correctly, the weapon's energy release will go directly to the path where the target is going. This requires practice to be done effectively. In the hands of an adept player, Fusion rifles can be quite devastating, capable of vaporizing targets if all beams connect.