From the Classics: Gusir's Gifts

"Ketil Trout took these arrows off Gusir, king of the Lapps," said Grim. "Because dwarfs made them, they bite anything they're told to."
...
Then Odd took one of Gusir's Gifts and shot it like the first one. The giantess put up her hand, but the arrow went straight through it into her eye and out through the back of her head.

- Arrow-Odd, (Anon., 13th century AD)

The three legendary arrows known as Gusir's Gifts have the ability to pass through almost any object, whether it be stone, flesh or armour. As such, they ignore any AC bonus granted by armour, tough skin, etc. but not by dexterity. Each arrow can pass through up to 5 feet of any solid object before it becomes bogged down. Furthermore, the wielder can whisper to the arrow before firing it and exhort it to bite one thing and not another. If the arrows are not given any specific instructions, they will tend to pierce flesh and armour but not walls or other objects.

Gusir's Gifts will never break after firing and thus can usually be retrieved and reused, so long as they do not land in some inaccessible location. The arrows can still be destroyed if a person or creature makes a deliberate effort to snap them in two.