Two-Face's Dual Pistols

"Two guns, bitch!"

- Two-Face to Catwoman

Two-Face used his Dual Pistols to commit the majority of his crimes, as seen during the execution of Catwoman in Batman: Arkham City. Two-Face used two guns most likely because of his obsession with duality.

Arkham City Incident
Two-Face used his Dual Pistols in the execution of Catwoman, and after his defeat, they could be found in the Solomon Wayne Courthouse and would resolve the riddle: "BANG! BANG! Order in the court."

Arkham Knight Incident
Two-Face's dual pistols, a half-acid damaged coin, and a rocket launcher used by him could be seen on display in the GCPD Evidence Room.

Trivia

 * Two-Face used two guns because of his obsession with duality, but was never seen using both at the same time.
 * When Two-Face shot at you in the courtroom, if you took cover behind the railing on the good side of the room, Two-Face would point his gun at you and wait. You could do that as long as you liked, but when you stopped crouching, he would shoot you immediately.
 * It was unknown why Two-Face left his other guns in the courthouse.
 * Interestingly, the guns changed from Arkham City to Arkham Knight. In City, they were based off of handguns. In Knight, they become revolvers, and according to other displays, the GCPD never returned the personal items of the Arkham City inmates they recovered. That change was likely a design oversight. However, because the revolvers turn up after Dent's defeat, it is more likely they were in his possession during the events of Arkham Knight, but simply weren't used.