Objects used and are in AoT(Firearms)

Firearms

Because firearms are unsuitable for dispatching Titans, they have not progressed very far technologically and are almost always overshadowed by the Three Dimensional Maneuver Gear. However, they are still regularly used by the Military Police and other human-to-human security relations. The Survey Corps also uses flareguns to communicate over long distances.

The type of firearm used is based on the flintlock mechanism, where a piece of flint ignites the powder and fires the gun, which must be reloaded after every shot. Currently, rifles (or muskets) and pistols are the only firearms seen in the story.

Although the firearms within the walls are low-tech, they do have some modern applications. During the battle of Trost, one of the most notable features of the firearm is the lack of smoke it produces. Indicating that it uses modern gunpowder, which creates a large flash, compared to black-gunpowder which produces a massive cloud of smoke when fired. 

Firearms are unable to kill Titans because they lack the power to punch through the nape of the neck (a Titan's weakness). Also, given a Titan's fast regeneration rate and the long amount of time it takes to reload a flintlock weapon (15-30 seconds), they are practically useless in dealing enough lasting damage to severely harm a Titan. However, they can shoot out a Titan's eyes and blind it until it regenerates them.