Izaya's Knife

Izaya uses a spyderco centofante 3 as his weapon of choice. Izaya is shown to have it hidden on his person. Izaya can deploy the knife very quickly and smoothly, showing his skill in blade play, as the centofante 3 is a non-spring assisted folder.

He is also shown throwing ordinary knives in the OVA.

History
Izaya is first shown using this weapon against the bullies harassing Anri, using it to cut and steal the purse of one of them. In almost all his confrontations with an offender, he is shown to use it as a means to defend himself. During High School, in the anime Izaya was shown using a flick stiletto blade to cut Shizuo.

Later, Izaya is seen in the Abadashi Arc sporting a new pocket knife (a Gerber Paraframe I) against Haruna Niekawa. Niekawa attempted to attack him while he was off guard for information about Takashi Nasujima. The knife is a silver non-spring assisted folding knife with a paraframe handle and a curved drop point.

He appears to be using a folding kukri while fighting Shizuo in the last episode of Durarara x2 Ketsu as seen in episode 11.