Outbreak Prime
Outbreak Prime is an exceptionally deadly weapon as it can quickly stack damage onto a single or group of targets via its two specific perks. The Corruption Spreads and Virulence all help spread SIVA nanite swarms which deal additional damage to foes and seek out other targets to infect. This allows a skilled and accurate Outbreak Prime user to quickly cut through ranks of advancing enemies, as the SIVA clouds can stack meaning you can have more than one out at a time, allowing for some additional chaos.
This is all nicely packaged in a lower impact, high rate of fire Pulse Rifle that gets the added benefit of having the Outlaw perk available for quick reloads after kills. For those looking to be a master of mob control in Destiny, look no further than the Outbreak Prime.