Knife

Knives are weapons that were used by some inmates and thugs in Batman: Arkham Asylum, Batman: Arkham City, Batman: Arkham Origins, and Batman: Arkham Knight.

Arkham Origins Incident
A Knife appears as a common weapon used by thugs in Arkham Origins.

Arkham Origins Blackgate Incident
The knives are used by some inmates.

Arkham Asylum Incident
While at Arkham Asylum, Batman had to face many prisoners called High Security Henchmen that used dual knives. Victor Zsasz tried to kill a guard and Dr. Penelope Young with his knife and carve marks into himself for each person that he killed.

Arkham City Incident
In Arkham City, the inmates still used knives, and actively tried to use them against Batman, Robin, Nightwing and Catwoman. Joker, (actually Clayface) could pick up a knife dropped by a henchman and use it against Batman in Joker's Fun Fair.

Arkham Knight Incident
Knives reappeared in Arkham Knight. They were one of the few melee weapons that could not be picked up from the ground, due to their lethal nature. In addition, Brutes wielded dual knives that were attached to their wrists. The Blade Dodge Takedown returned, but it was harder to successfully pull off.

Trivia

 * In the Combat Maps of Batman: Arkham Asylum, Victor Zsasz appeared using his two knives.
 * In Joker's Fun Fair in Arkham City, if Batman used the Blade Dodge Takedown on Joker, (actually Clayface) if henchmen are still around, it wouldn't work and Batman would takedown a completely different henchman.