Cryolator

The cryolator is a weapon in Fallout 4.

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.

Video on how to get the Cryolator early on!
 * The weapon can be acquired after Dogmeat (Fallout 4) becomes a companion. Proceed to Vault 111, head to the Overseer's Office and ask Dogmeat to search for an item for you. Dogmeat should break open the case and bring it to you. He will also be holding 200 cryolator cells.