Ammunition

Very Rare

Named: When chambering this enchanted round, the shooter chooses a creature within firing range that they can see. The bullet then becomes imprinted to that target, gaining advantage the attack roll against it and automatically turning a hit into a critical hit. The bullet gains disadvantage against every creature other than the target.
The bullet can be reset after seven days or if the designated target dies.

They say that a bullet has a name on it.
The weaponsmith behind this line of ammunition took this literally and enchanted every single one of them with magic that makes them aggresively home in on a designated target, making them the perfect tool for assassins.