Xargon

Xargon is a Platform Game developed and published by Epic Games (Then Epic Megagames) in 1993 for MS-DOS. The game consists of three episodes, the first of which was released as Shareware. The full game was released as Freeware in 2008.

The player assumes the role of Adventurer Archaeologist Malvineous Havershim. While studying ancient ruins in Madagascar belonging to an unknown ancient culture known only as the Blue Builders, Havershim falls prey to a mysterious gas and wakes up later to find himself Trapped in Another World.

In his dreams he is greeted by a talking eagle who informs him that the land he has entered is not a friendly one, and it is ruled over by a powerful and malevolent being known as Xargon. Havershim is thus thrust unwillingly into a quest to defeat Xargon, the only way he can ever go home.

Tropes used in Xargon include:

Abnormal Ammo: Malvineous' default weapon is a laser that he shoots out of... well, his chest. He doesn't seem to have an attack animation.
Cool Boat: In some water levels, Malvineous can pilot a bathysphere-like submarine that can shoot lasers in two directions.
Denial of Diagonal Attack: your default weapon only shoots straight ahead. The boulder "power up" shoots diagonally upwards, and has problems hitting enemies straight in front of you. You can use the arrow keys to move your laser bullets up or down, but this is mainly useful for hitting small targets and doesn't have the range of diagonal movement that the boulder does. Fireballs only shoot straight ahead, but they don't really need to move diagonally to kill everything.
Diary: In between levels, on the World Map, you come across little books that when touched present you with an entry from Malvineous' journal. He typically comments on the strangeness of the world he is in and it's bizarre and hostile inhabitants.
Game Breaking Bug: In the third episode, a glitch will occasionally prevent you from entering the castle where you get the Crown of Xarg and the final gate key. This also happens to be the last level before Xargon's castle, so you'd better hope you have a fairly recent save or you're screwed.
Jump Physics: You can fully reverse the direction of a jump in mid-air.
Lava Pit: This being a platformer, these are common.
MacGuffin: Each episode has three "Power Objects" which you must collect. Most of them are only fleetingly referenced in Mal's journal, with the Sky Crystals, Dark Ring of Terror, Amulet of Blue Souls, and Tinia's Lyre being the only ones that Mal seems to do much of anything with besides comment on.
Our Monsters Are Weird: The first enemy you face is a walking torso with one big sharp tooth. It gets weirder from there, aside from the occasional ill-tempered fish.
Power-Up: Pickups include hearts and fruits that heal you, upgrades to your default laser, as well as a throwable rock- nay, boulder, and a pickup that temporarily allows you to throw powerful Fire Balls.
Power-Up Letdown: the aforementioned boulder.
Sorcerous Overlord: Xargon.
Spikes of Doom: These are pretty common too.
Spiritual Successor: To Jill of the Jungle, which this plays almost identically to. Epic even referred to this game as the sequel at one point!
Super Drowning Skills: Stay out of the water!
Talking Animal: The talking eagle shows up a few times over the course of the game to give Malvineous further information. He's the only friendly NPC in the game.
World Map: Typically shows a linear path, but occasional branches appear.