Metalgun Slinger (メタルガン・スリンガー) is a 2002 game released only in Japan for GBA.
Billy MacDoleane (ビリー・マクダレーン) is the main character. In the beginning he is in trouble, but Mapiya appears and gives the Metalgun to him, which he uses to help his friends.
Mabel Munro (メイベル) is a friend of Billy that shows great concern for him.
Doc (ドク) is a friend of Billy and has mechanical skills. He has a big crush on Fay.
Fay (フェイ) is a woman that gives a Metalgun to Billy.
Mapiya (マピヤ) appears to be Fay's pet own.
Hawk (ホーク) is a guy with a Metalgun that works with Fay.
San Dansu (サン・ダンス) is the first boss. He is a friend of Billy, but is mutated into a bulky, green-skinned man by Peru Nogura and he tries to smash Billy. After the battle, Peru Nogura leaves his body and he returns to normal.
Babagu Gan (ババグ・ガン) is the third boss.
Sam Oldman (サム・オールドマン) is the fourth boss. He is the commanding officer of Peru Nogura.
Mainā Mainā (マイナー・マイナー. "Mainā" can be translated as "Minor", "Miner", "Meiner", ...), also known as the Killer Edge (キラーエッジ), is the fifth boss, a dangerous assassin with a really high bounty. He was mutated by Peru Nogura, and his form doesn't change after it leaves his body. After the battle, he tries to use Mabel as a shield, but is killed by Babagu Gan.
Dalton Nandoval (ダルトン・ナンドヴァル) is the seventh boss. He is a general that was well known in the Alamo as a hero, but now is used by Peru Nogura. He has two badges.
"Peru Nogura" (ペルノグラ, apparently derived from ペロネグラ Pero Negura, "Perola Negra", Black Pearl) is the main enemy, appearing as the second, sixth, and eighth boss in different shapes. Looks like some mutant or alien thing attacking cities that can enter on people to increase their power and control them.
Zeed (ズィード) is the ninth and final boss. The one behind Peru Nogura.
Tutorial. The stage change three times during game progress, becoming more challenging each time.
Navanhou (ナヴァンホー) (4 stages)
Gold Mountain (4 stages)