The Bazooka is a ranged weapon, and the only one of its kind. It is used in the intro to the game in Ruffleberg's Lab, then lost when the Hero arrives on Prehistoria and the Bazooka is damaged in the crash. Cecil Harvey finds and repairs the weapon on his own, and gives it to the boy when he arrives at Cecil's shop in Ebon Keep.
The Bazooka functions differently from other weapons. At 100% power, it fires a projectile forward, dealing a single hit to the first enemy it strikes. The Bazooka can be used without ammo, but it will not be able to fire. However, a glitch causes the player to never run out of ammo save for Thunderball ammo, so this is a moot point later in the game. The Bazooka is also unique in that it does variable damage, depending on the ammo equipped, and it never levels up.
The Bazooka has variable advantages and disadvantages over other weapons, particularly spears which are also ranged weapons. The Bazooka's shots have significantly higher base power than any other weapon, but unlike other weapons, the Bazooka does not increase in damage as the player levels up. Thus, at a point charged spear attacks will do more damage than the Bazooka can. The Bazooka does not need to charge to attack enemies at range, but below 100% power the Bazooka's melee attacks do very little damage, often only a single point, so the player cannot attack continuously. The Bazooka also has the drawback of launching the Hero backwards when fired.
Overall, the Bazooka is more effective against strong single targets, while spears are better for multiple weak targets, either for partial-power attacks that can kill them quicker, or for their charged level 2 attacks that can hit and kill multiple enemies. Note also that the Bazooka is incompatible with Energize, and cannot be fired while Energize is in effect.