Stinger Necklace

Two pre Hardmode effects folded into one slot: flat armor penetration, and a handful of bees that scatter out whenever something hits you, with a short honey buff for the regeneration. The bees are not much on their own, but they pick targets while you are busy retreating, and behind a Hive Pack they stop being trivial.

The bees and the honey buff come out of a shared pool. Wear a Honey Comb, a Bee Cloak, a Honey Balloon and this one at the same time and you get exactly the same swarm and the same buff as wearing any single one of them. Pick whichever gives you the most alongside the bees and drop the rest.

Armor penetration is different. It does add on top of a plain Shark Tooth Necklace, and a Sharpening Station on top of both pushes melee penetration much higher again. That bonus also applies to weapons which already ignore defense, such as the Crystal Vile Shard or the Blade Staff, so summoners get more out of the combination than they usually expect.