Guns

Guns are ranged weapons that fire bullets as ammunition.

In addition to ranged bonuses, guns also benefit from the Shroomite Mask, and are compatible with the Rifle Scope. Possession of any gun (or bullets) fulfills the criteria for the Arms Dealer NPC to appear.

Several other items are referred to as "guns" in-game (e.g. Space Gun or Water Gun), but none of these fire bullets or gain the above bonuses related to guns, nor will they cause the Arms Dealer to spawn. The Candy Corn Rifle and Coin Gun are considered guns despite requiring and firing a different type of ammunition.

The best modifier for guns is Unreal, with the exception of guns without knockback, whose best modifier is Demonic instead.

Types
There are currently different guns available in Terraria,  of which are Hardmode-exclusive.