Gamers have been enjoying Fallout 4 for a couple of weeks now, and modders are clearly getting to grips with the game’s secrets. The big find during week one was an infinite bottle caps exploit. We’ve just come to the end of week two, and someone has discovered a hidden weapon in the form of a harpoon gun.The discovery was made by modder xxdeathknight72xx while looking through the game’s code. Not only was the weapon discovered, it’s possible to unlock it for use. The most unusual feature is the reload animation including bubbles, which suggests this is a weapon that was meant for underwater combat.There are a number of reasons the harpoon didn’t make it into Fallout 4. The first being that there’s no underwater combat in the game. That may be because underwater combat is always terrible or Bethesda plans to add it (and this weapon) as part of some future DLC pack. It could also be the case that the development team ran out of time and this is a weapon that never got fully implemented and the bubbles in the animation is just an amusing bug.Whatever the case may be, it looks like a lot of fun to use based on the video footage above. It not only decapitates enemies, their heads spin on the harpoon if it ends up stuck in a wall afterwards.If you;d like to try the harpoon gun for yourself, then head on over to the nexusmods page for it.