Gawain

The Gawain (ガウェイン, Gawein), named after Sir Gawain of the Knights of the Round Table, is a prototype Knightmare Frame privately developed by Prince Schneizel El Britannia. It is unusual in that it is three times the size of most other Knightmares and features a double-seater cockpit, even though it doesn't need to be operated by two people. It also doesn't seem to feature Factspheres or an identifiable ejection system. The Gawain is equipped with an integrated Float System, making it capable of sustained flight. Its fingers are miniature Slash Harkens, and it features a pair of shoulder-mounted Hadron Cannons, which can emit continuous streams of destructive energy over prodigious ranges. The Knightmare is initially incomplete, and its Hadron Cannons fire erratically due to its blooming effect. The unit is perfected by the Black Knights' scientific mastermind, Rakshata Chawla, who uses her Gefjun Disturber technology to gain control of the Hadron cannons' erratic firepower. As a side benefit, the Disturber's natural disruption properties also render the Gawain invisible to radar. Its experimental Druid System analysis complex mark it as a powerful commander unit. Despite its strengths, the Gawain is a fairly slow unit, and as such is easily outmaneuvered by smaller, faster Knightmares.

Lelouch Lamperouge and Kallen Kozuki steal the Gawain in episode 19 of the first season in order to escape from the Kaminejima Island ruins. Despite the amount of new technology consequently lost, Schneizel dismisses the Gawain's theft, considering it to be a mere "experimental subject". After its technology is perfected, it becomes Lelouch's and C.C.'s personal Knightmare; C.C. handles the piloting while Zero operates the weapons and issues orders.

The Gawain later proves instrumental in Zero's plans during the invasion of the Tokyo Settlement, single-handedly wiping out the totality of Britannia's air support in the area. The Gawain is lost during a duel with the Siegfried, a powerful Knight Giga Fortress, when C.C. uses its Slash Harkens to entangle the Siegfried and drag them both into the crushing depths of the ocean. Though the frame is damaged beyond repair, its Druid System and Hadron Cannons are salvaged. Both technologies are incorporated into the Black Knights' flagship, the Ikaruga. It is also adapted by Rakshata to control the Absolute Defense Territory system of Zero's personal Knightmare, the Shinkirō.

Nightmare of Nunnally
The Gawain is also shown as Zero's personal Knightmare Frame in the Nightmare of Nunnally manga. In this series, Zero expands his armor to materialize the Gawain, and then controls it from within. This version looks visually identical to its anime counterpart.