It is the absolute single hardest hitting weapon in the game. Shot for shot, no other weapon outdoes it. There are many imitators but there is nothing as powerful in the game currently.
Aside from damage, it was the first exotic that was unanimously agreed to be truly exotic; both in look and function.
It has the personality of a monster and grants an ego to match. I've seen confidence soar in a raid when a Gjallarhorn is utilized to its full potential, which is easy because it requires a simple point and click. The gun is the virtual 'Big Dick Complex', it is the boss ender, it is the crutch you rely on to carry a weak team.
Sorry I can't recall original posters tag, love the quote tho :)
English