It is widespread but it's not variance in message and interpretation.
One can argue about who has the "cutest" monkey or the "spookiest" ghost but they are still a monkey and a ghost.
A water pistol is not the same thing as a "realistic" gun.
What do you think would happen if some one sends a text from an iphone saying "war in the school parking lot bring your [gunemoji]" while being used to the water pistol emoji and some one gets the same message with a realistic gun emoji?
Having artistic variance is fine, but there are guidelines, the emoji still has to be universally recognizable and not misleading a water pistol is not a gun.