When Bungie first addressed weapon balancing in Destiny, they said Exotic Weapons are designed to "look, feel, and sound overpowered." While I think the "feel" of some of these weapons is a bit debatable, there's no denying they look and sound pretty darn amazing.
To date, I've only received two Exotic weapons — Bad Juju and Invective — but what happens when the RNG (random number generator) Gods bless you with numerous exotic weapons? Sweet music to your ears.
[EnderGamma via Bungie]