The Eye of Cthulhu

Mothron only turns up in eclipses that happen once Plantera is dead, so by the time this yoyo is farmable you already have a shelf of hardmode melee options and a reason to be picky. It earns the slot anyway. The throw hangs out at the end of its string and keeps working while you hold the button, which lets you park damage on something and spend all of your attention on not being hit.

Any yoyo feels like a worse sword until you have a counterweight and a string upgrade on it, because the extra projectiles are most of the damage. A Yoyo Bag rolls all of that into one slot. Skip that step and you will conclude this thing is bad, which is the usual mistake with the whole weapon class.

Modifiers get bolted onto the front of the article rather than the noun, so a good roll can leave you holding a Keen The Eye of Cthulhu. It also shares a name with the first boss most players ever fight, which makes looking it up briefly confusing.