The Black Knight

The Black Knight is a in Fallout 76.

Background
According to its entry data name and model name ("ATX_Sten"), it is based off the "Sten gun", a WWII weapon that has previously appeared in Fallout Tactics.

Oddly, it seems to be chambered to .308, which is a unusually big caliber for a SMG. Despite it being historically a SMG, according to its keywords, it will use hunting rifle animations. However, this could all just be placeholders until the actual stats are set.

As the second part of the entry name implies (ATX), it will only be obtainable through the Atomic Shop, most likely crafted like other weapon model ATX in the Atomic Shop.