Heavy Barrel

Heavy Barrel is a 1987 overhead run and gun arcade game by Data East.

Terrorists have seized the underground control complex of a nuclear missile site, and it is up to the player to infiltrate the base and kill the enemy leader. Players begin armed with a laser gun with unlimited ammunition and a limited supply of grenades. Improved weapons and grenade powerups are made available within the game, either in plain sight or within crates that must be unlocked using keys. Additionally, crates may contain orbs or one of the six pieces of the Heavy Barrel superweapon. Like SNK's Ikari Warriors, the original arcade version featured 8-way rotary joysticks.
The name of the game is from an in-game weapon. The Heavy Barrel is found in six pieces and is an energy cannon capable of destroying any enemy in the game with a single shot (except the final enemy, and possibly one other boss that may have required two shots). The weapon has a wide arc of fire and can be fired as fast as the player's trigger finger permits, but after thirty seconds its use is exhausted, at which point the bearer reverts to his previous weaponry. Best used to get past tough bosses, the weapon could be built several times in a single game (probably three or four times). In a two-player game, whoever collects the sixth piece is equipped with the Heavy Barrel.