As Arma's final and most powerful weapon, the Omega Cannon fires an arc of multiple lasers from her back that home in on nearby targets inflicting area damage from the ensuing explosions. The strange fact that the Omega Cannon actually fires from behind makes it advantageous to actually turn away from an enemy to use it in most cases. (The beams really start from the front of Arma's sprite, so you can "punch" with it if you need to.) It can also hit airborn enemies with ease, as well as shoot around corners, making it by far Arma's most versatile weapon. Surprisingly despite its power, the Omega Cannon uses only half a unit of ammo, making reloading problems relatively minimal.
Due to the large amount of Salamander Scales involved in its creation, the Omega Cannon is one of the easier final pieces of equipment to get the maximum +15 bonus on.
Some boss fights with Omega Cannon are quite tricky. In the Tielle boss fight, missiles don't attack boxes themselves. To destroy the box with the Omega Cannon, you need to stand backwards to it and close enough. Attacking Electrojelly with Omega Cannon is not that simple, because missiles aim into the center of it, where Electrojelly is invulnerable, but it can be killed. Arma and Griff after recieving two hits become invulnerable, so killing them with Omega Cannon isn't quick (though weapon's attack is high, attack of every beam is rather low). In the second Griff fight Omega Cannon's beams may aim to Archdevil's Arm (if Arma stays close to it) dealing 0 damage. Because of this, it is strongly recommended to take a second weapon with you when using Arma in the Crystal Nightmare boss rush.