Slings are basic one-handed ranged weapons which can be used by nearly all classes, expect monks, as long as they have a mere Strength of three points. Slings need bullets as ammunition, but this weapon is very seldom used by enemies, which means the party needs weapon stores for their supply of bullets. The amount of different bullets is far less varied for this type of ammunition, as for other ammunition. Most slings have a rate of fire of 1 per round, which is quite slow for ranged weapons.
In general, it's wiser for rogues and warriors to specialise in other ranged weapons, while mages or clerics can become at least proficient in slings.
Slings have existed since the beginning of recorded history. The basic sling consists of a leather or fabric strap with a pouch for holding the missile. The weapon is held by both ends of the strap and twirled around the wielder's head. When top speed is attained, the missile is launched by releasing one of the strap's ends.