Throwing is a skill used primarily in Adventure Mode. The thrower skill determines the accuracy and damage of thrown objects. Note that any object can and will cause serious damage when thrown, including socks, roaches, and even water.
 Throwing in Fortress Mode
In Fortress Mode a dwarf who is tantruming may pick up and throw an object. Doing so gives the dwarf experience towards throwing. Otherwise, dwarves will never use throwing in Fortress Mode.
 Throwing in Adventure Mode
In Adventure mode throwing is an excellent way to roll the dice before close-combat, essentially giving the chance for the opponent's vital organs or extremities to be damaged (plus any bonus that may come with the damage - for example, sightless monsters or weaponless guards). Furthermore, anything can be used as a weapon. Silt, pebbles, and vomit have been witnessed colliding with opponents with devastating results (two or three handfuls of dirt can take down a wolf, for example).
At the moment, an excellent way to level up your throwing skill is to collect many items and throw them directly under you. This, combined with an endless supply of vomit, soil, or small rocks, can increase your warrior's attributes and your throwing skill to Legendary in about ten minutes. It is unknown whether this will be tweaked in coming releases.
Another amusing throwing bug is that throwing is not proportionate to adventurer strength. A human throwing a dragon corpse a few tiles is perfectly possible, although it may or may not be as efficient as just throwing a weapon.
Most things you throw will do bludgeoning damage, however there are some items that you can throw that do different kinds of damage. Although it's not as effective as using a bow/crossbow, you can throw arrows and bolts and it will do piercing damage (and, as an added bonus, you will be able to pick up the ammunition afterwards). You can also throw things like swords and axes and they'll do slashing damage.