The Eos Auto Shotgun is a community-made weapon created by darkstar 1[1], added in Version 1.32. It's low power is compensated by having the highest rate of fire of all shotguns.
Location
The Eos Auto Shotgun does not appear in the campaign, and therefore is exclusive to custom maps created with the Advanced Level Editor.
Trivia
The Eos Auto Shotgun has the lowest power value of all weapons.