Cryolator

The cryolator is a weapon in Fallout 4.

Background
A part of the Vault 111 experiment, besides using cryosleep pods, was to find other uses for cryotechnology, primarily using it as a weapon. Conceptually, it's a Flamer that shoots ice.

Locations
Inside Vault 111, in a display case in the Overseer's Room behind a Master level lock. It cannot be picked up at the beginning of the game due to the inability to pick Master level locks before exiting the Vault. Interaction with the case prompts a line from the Sole Survivor, saying that he/she will return for it later. An entry on the Overseer's Terminal in the same room can be found detailing the weapon and why it was built.

Exploits
Once you have found Dogmeat (Fallout 4) you can return back to Vault 111 and go into the room with the Cryolator, there you can tell Dogmeat to fetch you an item. Dogmeat will go and pick up the Cryolator from the case and bring it to you.