In fights where you are defending, the Ray Gun is the best choice to ward off invaders if there are other people with them. Despite the damage, the Ray Gun takes a long time to load which is the vulnerable point of the weapon. Because of this disadvantage, the Ray Gun C-01y is used for sniping, or defending most of the time.
If you to be happen to be in multiplayer, it will fire 2 rays, while in singleplayer, multiple rays depending on upgrade leveI.
Ray Guns can first be found in Level 6, on the crashed ship. Fully upgraded Ray Guns are carried by the Protaginist's clones in lever 26, Civil Security Bosses in Level 40, and Noir Lime carries another fully upgraded Gun in Level 41. In that level, 3 Usurpation Destroyers also use Ray Guns at Upgrade Level 2.