eva 00

A mecha in Neon Genesis Evangelion, piloted by Ayanami Rei.

Eva-00 was the first operational Evangelion. Being a prototype, it was not originally equipped for combat, but was later upgraded and brought into battle against the Angels.
Eva-00 is the most unstable of the Evangelions, going wildly berserk on two occasions: once during its activation experiment with Rei, and again during its interchangeability experiment with Shinji. Despite these incidents, Rei retains good control over the Eva once it is operational, using it successfully in quite sensitive tasks such as handling the Lance of Longinus on two occasions, and both fetching and firing the SDF's positron cannon.