The flares fired by the Flare Gun give as much light as a torch, stick to surfaces (in the same way as Sticky Glowsticks), and are not doused by water, making this item a very handy tool for exploring.
Although Flares have a high chance of inflicting the debuff "On Fire!" and can pierce an infinite number of mobs, this item is still not particularly well-suited to use as a weapon due to the very low amount of damage it inflicts.
The Flare Gun doesn't count as a gun for the purpose of spawning the Arms Dealer, and cannot be reforged.
Like Glowsticks, flares fired by this item will disappear upon exiting a world. Additionally, disconnecting and reconnecting to a server will result in being unable to see previously-fired flares on the ground, even if they are still there.
The Flare Gun emits light underwater when held. As such, it can be used as a substitute for Glowsticks.
Firing the Flare Gun at another player with PVP enabled will cause the player to gain the "On Fire!" debuff on the screen of the player who fired. The burning player's health can be seen decreasing if the cursor is put over him or her, but the health will update to the real amount every few seconds until the debuff ends.
On iOS, if the Flare Gun is shot, the gun will become invisible and the player will see the Flare's flame as if they were holding it.