Modders adding weapons to Fallout 4 is to be expected. Modders uncovering hidden, since-deleted weapons is a horse of another color. Yet, that is exactly what modder xxdeathknight72xx's mod did. After pouring through Fallout 4's PC code, xxdeathknight72xx was able to discover and unlock the Harpoon Gun.

The secret weapon, which overrides the "Railway Rifle," allows players to skewer ghouls and raiders with harpoons. The animation (though low-res and choppy) shows bubbles coming from the harpoon, suggesting that it was originally supposed to be used in underwater combat. Or, perhaps, underwater content is to come?

Check out the below video of YouTuber Tyrannicon testing out the Harpoon Gun: https://www.youtube.com/embed/kiC8oCf0GAk