The Doomslayer is a sword you can get in Goat Simulator 3 that references the same in Doom.
It’s just a replica and doesn’t have any real ability attached to it. However, it’ll allow you to complete an event / quest.
Here’s how you can get the Doomslayer sword in Goat Simulator 3.
The Doomslayer sword’s location is shown in the map below at Coscon, marked by the goat symbol.
You’ll find the sword stuck in stone and there’s a guy nearby who cosplays as a Super Saiyan from Dragonball Z.
Lick the sword and drag it away to get it. The cosplay dude will try to chase after you but you can just knock him down.
The event ends here. It’s a reference of both Doom and King Arthur’s sword.