
Shooter / Arcade / Action / Science fiction
Xeno Crisis is an arena shooter in which one or two players take control of battle-hardened marines embarking on a deadly mission to confront an alien menace and get home alive! Run and gun your way through thousands of adversaries as you explore the devastated research outpost, searching for survivors, and ultimately facing the origin of the outpost's demise. Outpost 88 is divided into seven distinct areas, each being randomly generated with each play, meaning that your strategy must evolve on the fly if you're to succeed in your mission. Collect dog-tags from vanquished enemies to upgrade your equipment between areas and look out for special weapons which will give you a momentary advantage.

Shooter / Adventure / Action / Science fiction
Halo 2600 is an action-adventure video game developed for the Atari 2600 video game console, inspired by the Halo series of video games. Halo 2600 was written by Ed Fries, former vice president of game publishing at Microsoft, who was involved in Microsoft's acquisition of Halo developers Bungie Studios. Fries decided to create a version of Halo for the Atari 2600 after being inspired by a book called Racing the Beam: The Atari Video Computer System by Ian Bogost and Nick Montfort. The Atari 2600 had such limited RAM, only 128 bytes, that drawing Master Chief was difficult, and creating a game with other characters was even more so. Fries later stated that making the game taught him that constraint is sometimes a fuel for creativity.

Shooter / Platform / Action / Science fiction
Homebrew version of Mega Man 2 for TurboGrafx 16/PC Engine
Developed by fjsantos in 2003, this is a Space Invaders clone developed using DragonBasic.

Shooter / Indie / Action / Science fiction
The sky is falling! The sky is falling! Your base of operations is the last line of defense against an imminent disaster. Big rocks and lil rocks are pounding the earth. Making matters worse, extra terrestrials or some rogue government are sending over spinner missiles and pulsar bombs designed to end your day and make sure you and yours can never phone home again.

Shooter / Action / Science fiction
Oystron is an action game in which the player controls a ship using the joystick controller, firing at enemies and collecting pearls dropped by "space oysters". The player's ship initially appears on the left side of the screen, and enemies attack from the right. Shooting the space oysters reveals a pearl; the player then collides with the pearl and brings it to the "pearl zone" on the left side of the screen. Other enemies appear that attempt to steal the pearls. Collecting eight pearls earns the player a bomb. At the end of each level, a boss named "Oystron" appears; the player can defeat the Oystron by placing a bomb in its path, or waiting until it changes into a space oyster. Following the appearance of the Oystron is a warp phase, in which the player travels at high speed and must avoid colliding with enemies. The player is given four ships at the beginning of a game, and earns an additional ship every 4000 points

Shooter / Platform / Action / Science fiction
Unofficial homebrew port of Mega Man X for the Sega Genesis/Mega Drive.

Shooter / Action / Science fiction
DsDoom 3 is a 32-level total conversion for Doom II created by Sniper 109 for Boom-compatible ports. DsDoom 3 was created to maintain compatibility with the DS Doom port, which was created to play Doom on Nintendo DS handheld consoles and is based on PrBoom. As the name of the WAD and the title screen indicate, the mod is heavily based off Doom 3, with its weapons and most of its enemies being closely modeled after that game, featuring new and unique behaviors through DeHackEd.