Kagemitsu G4

«Kagemitsu G4» is a light saber owned by Kirito in Gun Gale Online. Currently, it is under Sinon's possession.

Gun Gale Online
Kirito just bought Kagemitsu G4 because it's the only thing he found that resembles a sword, since he was used to fight with swords in SAO and ALO.

Trivia

 * It was introduced to the game as a whim of the creators to resemble the movie Star Wars.