Princess Cannon

The Princess Cannon is a special weapon in Splatoon 2. It is not part of any main weapon's set, and is instead only available in the final Shifty Station layout, MC.Princess Diaries, where it appears in the middle of the stage when there is one minute left until the battle ends. It is similar in appearance and function to the from Splatoon, although the beam is much larger and it takes a little longer to charge up.

Octo Expansion
The Princess Cannon is used in the final Turf War battle against Commander Tarter in the Octo Expansion.

After the Turf War, the NLS Statue will still fire its laser. Pearl will use the Princess Cannon to counter the laser. As she fires the Princess Cannon off, a screen will pop up, showing the turf war percentages. Pearl will win by 888.8%, and the meter will crack like it will in Ranked Battles.