Magical:
Arrow of Rock Piercing - Originally 2E (I converted it a bit, but it may still need some tweaking by you and your DM for use).
This arrow is made of a special, magical metal. Upon striking non-living rock, the arrow embeds itself with only the last 6 inches of the arrow shaft exposed. A small metal ring is set into the rear of the arrow, to which can be tied a thin line or cord (or silk rope). If an archer with an
Arrow of Rock Piercing encounters a deep chasm with no way across, they need only tie the cord or rope to the end of the arrow, and shoot the arrow at a suitable rock structure on the side of the chasm opposite the archer. (A suitable Rock structure is any stone or brick material capable of supporting the weight of anyone hanging from it by a rope.) The arrow automatically imbeds itself upon striking non-living rock. If the rock structure is of adequate size (normal target size) and within range of the bow (with normal range penalties), any roll result other than a 1, should result in a successful hit. If the target is smaller, adjust the roll accordingly.
The
Arrow of Rock Piercing is reusable; in order to retrieve the arrow, the archer simply grasps it, speaks the arrows command word, and pulls it from the rock as easily as if it was embedded in butter. Alternatively the arrow may also be used by grasping the arrow in hand, speaking the command word, and then stabbing the arrow into non-living rock. After the arrow is released, it is firmly fixed into the rocky material and can be used as above. It can then be removed again by speaking the command word and pulling it out of the rock.
When used against any material other than Rock, the arrow acts as a normal, non-magical arrow. At the DM's discretion, the arrow may provide a bonus when used against a living or animated target composed of stone (Stone Golem, Crystal Warrior, etc.), and may also instantly slay any petrified creature.
Some other ideas (you'd need to flesh them out)
Arrow of Silence - Arrow has a permanent area of silence around it when drawn from a quiver or a command word is spoken. The area of silence negates any sound of the arrow being fired (the creak of the bow, the "twang" of the string, etc.), and the sound of the arrow striking its target. Highly useful when stealth is desired, or for negating, from a distance, a creatures ability to speak or use a sound based ability or attack.
Arrow of Darkness - Upon striking, the target and a set area around it are enveloped in magical darkness.
Arrow of Paralyzation - Upon striking, the target must make a save (I know that's older edition speak, just convert to 4E), or be paralyzed (4E conditions: Immobilized, Helpless, or both?).
Non-magical arrows:
Signalling Arrow - a blunt arrow that has a ball-shaped tip (wooden). The ball is carved so that when it travels through the air, it makes a sound like a specific kind of bird in flight (a hawks call, etc.).
Frog-crotch - used for cutting ropes.
