The Wave Motion Gun (波動砲, Hadou Hou) is a weapon which appeared in the Uchuu Senkan Yamato science fiction anime series from the 70s.
This special weapon is the "trump card" of the Space Battleship Yamato.
The Wave Motion Gun functions by connecting the Wave Motion Engine to the enormous firing gate at the ship's bow, enabling the tachyon energy power of the engine to be fired in a stream directly forwards.
Enormously powerful, it can vapourise an entire fleet of enemy ships with one shot; however, it takes a brief but critical period to charge before firing.
A little known fact is that the creator of Street Fighter created Ryu's "Hadouken" attack inspired by the Hadou Hou.
The main cannon of the SDF-1 from Macross was also inspired by this weapon.