The Laser is a recurring weapon from the 1940 series. It is usually represented by a double shell icon. On later games the Laser was renamed to Super Shell, though it is unrelated to the weapon of same name which appears in 1943: The Battle of Midway.
The Laser originally appeared in 1943 as a secret weapon, which can only be obtained by finding the very rare Lucky Cat item or by using cheat codes. Since it was a secret weapon it was tremendously powerful and had infinite ammo, piercing through enemies and making short work of large enemies and bosses. It returned in 1943 Kai: Midway Kaisen as a regular weapon, replacing the Auto. It was severely toned down, but was still powerful, retaining it's piercing properties.
In 1941: Counter Attack the Laser returns, but is renamed to Super Shell. It works much like before, piercing through enemies, and when charged would fire a salvo of missiles forward. It appears again in 19XX: The War Against Destiny, this time as a thick blue laser which pierces through enemies but is fairly slow. It is the preferred weapon of the Kyushu J7W Shinden, firing two laser beams when maxed out with it. The laser would return again in 1942: Joint Strike, working much like it did in 19XX.