Wasp Swords are extremely powerful melee weapons obtained from breaking Wasp Spawners inside the giant roof-mounted Wasp Nests. They aren't easy to get, but they are worthwhile.
These swords deal +10 damage (totalling to 11 damage, aka 5 and a half hearts!) as well as have a chance to inflict Poison on their victim. It is unknown how enchantable they are.