Sniper shotgun 

A shotgun so accurate that it can be used at mid to long range distances, where you would typically use a sniper rifle.
In videogames typically occurs when the shotgun is just made too accurate or may be specifically implemented as a joke. Often comes with a high magnification scope (or the wielder may choose to attach one).

The devs made that new gun an absolute sniper shotgun. It can still hit all pellets at 50 meters, I better attach an x4 scope on it!

Sniper shotgun by Darth Dan December 12, 2018

Sniper Shotgun 

When players utilize in-game sniper rifles and use them as if they were assault rifles or shotguns, or when a sniple rifle is in the conditions to be used as a sniper shotgun.

Player 1;Team 1: Everytime I try to get past that point, some guy keeps coming out and sniper shot gunning me!

Player 2; Team 2: Every time I sniper shotgun somebody with this bolt action sniper rifle, they die in a single hit!

Player 3; Team 2: That Mosin Nagant you have is a perfect sniper shotgun.

Sniper Shotgun by Marlowe Preston May 25, 2010

Snipe with a Shotgun 

To attempt to do something where success is extremely unlikely or impossible. Sniping is hard, and using a shotgun makes the job almost impossible. Use it when describing a situation that is the same as pissing into the wind

Guy 1: Hey, check out that girl over there. Think I can get her?
Guy 2: No offense but you might as well try to Snipe with a Shotgun.

Snipe with a Shotgun by Royce McMillan May 26, 2010