Guide Voodoo Doll

The Guide Voodoo Doll is an accessory that can be dropped by a Voodoo Demon in the Underworld. It has a resemblance to the Guide.

When this item is equipped as an accessory, it becomes possible to kill the Guide with weapons. If the item is destroyed by Lava in the Underworld, it will kill the guide and summon the Wall of Flesh. If the item is destroyed while there is no living Guide, the Wall of Flesh will not appear.

Before the Wall of Flesh is defeated, the Arms Dealer's dialogue is replaced with the line "I heard there is a doll that looks very similar to [Name of Guide] somewhere in the underworld. I'd like to put a few rounds in it.", hinting at the fact the doll has to be destroyed to continue progression. The Nurse can also say, "How many times will [Name of Guide] come in with severe lava burns?", hinting that the doll has to be thrown in lava.

Regardless if the Wall of Flesh is killed or not, the Guide will always respawn after being killed.

Trivia
*It's also just a normal saying, and it more than likely not a quote or reference.
 * The tooltip "You are a terrible person" is a quote from GlaDOS from the game Portal 2.