Projectile weapons fire something out in order to attack from a distance, allowing the user to
avoid having to care about their opponents being
Made of an Element, and so on (though they
don't really help against foes who can hide
underground). Most projectile weapons are
further distinct from other types of weapons in that the damage dealt by their projectiles is
not based on the user's stats, but rather the weapon itself, and often the kind
of ammunition loaded in. They include the familiar bow and
arrow, wherein it's the bow instead of the arrows that determines the damage done, as well
as guns: rifles, which are pretty basic; machineguns,
which fire multiple shots per turn, but each shot usually deals little more than 1 damage;
bazookas, which deal a lot of damage, but usually can only have one shot loaded in
them at once, meaning they take two turns to reload and fire each time; and pistols,
which are functionally just wimpier rifles.
Besides those and some random extra stuff, I've also written up all of the weapons from Cave Story, which have their own unique mechanics based on how they work in that game.