A simple console command will teleport you into Fallout 4's secret "treasure" room.
While most gamers are content to play through games "the right way," sometimes it is fun to be a cheaty mccheaterson and find the coolest and funnest ways to break the game. In Fallout 4, a secret "treasure room" has been discovered, and is an absolute cheater's delight, containing one of every single item in the game. Want a fat man launcher? Done. How about a full set of top tier armor? Yep. Maybe you just need some god-damn duct tape for a weapon mod? It's all here, and it's fairly simple to get to - provided you're running the PC version of the game.
To get to the secret item room, simply open up the game's console by pressing the tilde (~) key and type the command "COC QASMOKE". You'll be instantly teleported to the room, which contains chests full of every single collectible item in the game, a dozen or so full suits of various types of Power Armor, and one of every crafting station so you can experiment to your heart's content.
The QASMOKE room is somewhat of a staple in Bethesda games, appearing in almost the exact same capacity in 2011's Skyrim. It appears to have been put in as a way for playtesters to get their hands on every single possible combination of items in order to test them for bugs.
For the moment, it looks like you can only get to the room in the PC version of the game, as there's no way to get to the console in the Xbox One or PS4 versions.
To get out, simply use the COC teleport console command to teleport you back to another part of the wasteland, for example, "COC REDROCKETEXT" will send you to the Red Rocket gas station.
Source: Game Informer