From the Super Mario Wiki
The Gunner Guy is a type of Snifit that appears in Bowser's Castle in the game Mario & Luigi: Superstar Saga. Because of its very long snout, which serves as a gun, a Gunner Guy can hardly move by itself, requiring a Shy Guy clad in army camouflage to help him during battle.
The Shy Guy will push the Gunner Guy up to its target before firing. If the Shy Guy simply pushes the Gunner Guy, the latter will fire a cannonball, which will fall onto the ground and roll very slowly towards the designated brother. If the Shy Guy hops before the attack, the Gunner Guy will fire a quick projectile that will fly straight at its target. Both attacks can be dodged by jumping. These enemies are healed by fire, but are weak to thunder.
Names in other languages
||From Olfiti (Snifit) and Hormiguero (Anthill)
||Pun on "sniper" and "Maskass" (the French name of the Shy Guys)