A 1989 PlatformGame for the UsefulNotes/NintendoEntertainmentSystem, developed by Aicom.
Amagon is a run-of-the-mill [[SemperFi Marine]] who has the unfortunate luck of landing on a deserted island, armed with only his trusty machine gun and 300 bullets. Said deserted island is overloaded with spiders, scorpions... and [[HalfHumanHybrid anthropomorphic beasts]]? Who are, sure enough, all out to get Amagon. The good news is, Amagon spies a boat on the crescent-shaped island, which could lead to his escape. The bad news, of course, is that it's on the complete opposite end of the island from where he lands. Though one more bit of good news for him - there's an item to be found on the island called the Mega-Key (well, Mega-''Ki'' is more likely, since the icon isn't actually a key...), and by getting it, he can turn into a [[SuperMode musclebound-behemoth]] whose punches pack a wallop well beyond what his gun can do.
!!This game has examples of:
* BigBoosHaunt: Zone 4. If it's creepy music and dark colors didn't give off enough of a vibe, it has weird ghost things, [[OminousOwl spooky owls]], ghostly flames, and disembodied heads. The boss is a skeleton monster.
* BookEnds: Since the island is crescent-shaped, you can see the opposite shoreline at the beginning of the first stage and the end of the last.
* CastFromHitPoints: The most powerful attack in the game is a laser arc that Megagon can shoot from his body, at the cost of one of your hit points.
* CutAndPasteTranslation: The original Japanese game was called ''Totsuzen! Macho Man''. In that game the protagonist is a scientist named Jackson, capable of transforming into a strong man using the Macho Max drug he invented. Said drug was stolen by the enemies of Monster Island (and may explain the number of HalfHumanHybrids running about). The North American release changed the main character into a Marine named Amagon and dropped the rest of the plot.
* DeathMountain: Zone 5.
* DeathThrows: Turning towards the screen and throwing his hands up, Mario-style.
* DemBones: The Boss of Zone 4, The Skeleton Monster.
* EmpoweredBadassNormal: Amagon as Megagon; Amagon is a trained Marine who can mow down an army of hostile animals and beast-men with [[MoreDakka enough bullets]]. Megagon is the same Marine given a super-strong super-tough super-body.
* GreenHillZone: Zone 1.
* HalfHumanHybrid: Each level has a MiniBoss that's a mashup of a person and a large, powerful animal.
* JungleJapes: Zone 2.
* TheLostWoods: Zone 4.
* NintendoHard: You die in one hit, you have limited means to defend yourself, and enemies love to come in swarms. Yeah, this game isn't easy.
* NoPlotNoProblem: You're stranded on a deserted island and your rescue ship is on the other end. Everything along the way is trying to kill you. Go!
* OneHitPointWonder: Amagon. One of the reasons that Megagon form is so useful.
* OurCryptidsAreMoreMysterious: The alien FinalBoss is the Flatwoods Monster in all but name. What it's doing in the south Pacific is anyone's guess.
* PalmtreePanic: Zone 6.
* PistolWhipping: Amagon's attack when he runs out of bullets.
* PowerUpMotif: Megagon has his own theme, which will usually override the current music. (Zone 4 is the exception: its spooky music continues to play even when Amagon turns into Megagon)
* RiverOfInsanity: Zone 3.
* ScoringPoints: Valuable for once, because each 5000 points you have when activating the Mega-Key results in an additional hit point for Megagon, up to a maximum of 70,000 points to convert into 14 hit points.
* SoNearYetSoFar: The ship to take Amagon to safety is clearly visible in the distance right at the start of the game, but you have to fight your way all the way across the island to get to it-- presumably the open water is even more hazardous to swim across, seeing how the rivers are filled with deadly fish.
* SuperMode: Megagon.
* TransformationTrinket: The Mega-Key.
* WhamLine: [[spoiler: "Watch out for outer space invaders."]]
* WhenTreesAttack: Devil Tree, boss of Zone 2.
* AWizardDidIt: The game implies that the island's strangeness is due to the influence of [[spoiler: an alien that is the FinalBoss]].