Crystal Horn - If the player has Luxin Cannon, Luxin Cannon gets three crystal shots at the end of every magazine, and the crystal bursts into many more crystals. Additionally, when an enemy is killed with the Unicorn Horn, they explode into Luxin Cannon projectiles.
Double Rainbow - If the player has Stuffed Star, while Stuffed Star is active, five Unicorn Horn beams are fired from the player in all directions.
If the player has Helix Bullets the 2 rainbows fired will follow the same path, and not lose their homing property, unlike most other homing guns with Helix Bullets.
The beam, and the unique music that plays while firing, are a reference to Space Unicorn.
The fact that holding this gun increases curse might be a reference to the Harry Potter franchise, where killing a unicorn will curse you for the rest of your life.
Hearing the song that plays while shooting the gun in its entirety requires unloading almost the entire magazine in one continuous shot, spending 480 points of ammo before the song loops.