Badger's Hat

Both the Eye of Cthulhu and the Wall of Flesh have to die within the same in-game day, counted evening to evening. Nothing about a normal playthrough lines those up, so getting it means starting a world with the intent: a rushed early kit, an early night boss kill, and a route to the underworld already planned.

It copies a streamer's hat, whose green section disappears on camera because of his green screen. The item reproduces the bug rather than fixing it, so the green part blinks out at random while you wear it. The second half of the tooltip borrows the phrasing used on developer items.

It wobbles as you walk, it shows up above your head on the map, and wearing one in the armor slot alongside another in vanity stacks them into a single taller hat.