Red Eclipse AlternativesFirst-Person Shooters and other similar apps like Red Eclipse

Xonotic is a free (GPL), fast-paced first-person multiplayer shooter that works on Windows, OS X and Linux. The project is geared towards providing addictive arena shooter gameplay which is all spawned and driven by the community itself.

Unreal is a series of first-person shooter video games developed by Epic Games.

Quake is a classic first-person shooter game that revolutionized the genre with its fast-paced action and innovative multiplayer modes. Originally released in 1996, it continues to be a beloved title among gamers.

OpenArena is a community-produced deathmatch FPS based on GPL idTech3 technology. There are many game types supported including Free For All, Capture The Flag, Domination, Overload, Harvester, and more. There are 17 unique player models to choose from and 12 weapons.

Cube 2: Sauerbraten is a free multiplayer/singleplayer first person shooter, built as a major redesign of the Cube FPS.

AssaultCube is a free, multiplayer, first-person shooter game, based on the CUBE engine.

Taking place in realistic environments, with fast, arcade gameplay, it's addictive and fun!

Warsow is a completely free fast-paced first-person shooter (FPS) for Windows, Linux and Mac OS X, set in a futuristic cartoonish world where rocketlauncher-wielding pigs and lasergun-carrying cyberpunks roam the streets.

Unvanquished is a free, open-source first-person shooter combining real-time strategy elements with a futuristic, sci-fi setting. It is available for Windows, Linux, and Mac OS X.

Halo is a science fiction, first-person shooter video game series, that centers on an interstellar war between humanity and a theocratic alliance of aliens known as the Covenant.

Freedoom is a WIP a complete free content game based on the Doom engine. It's not an engine, but it's replacement game data with entirely original content, Compatible with a majority of game mods made for Doom. Comes in Three Flavors~.

Serious Sam is a first-person shooter video game series that follows the adventures of protagonist Sam "Serious" Stone and his fight against the forces of the notorious extraterrestrial overlord Mental who seeks to destroy humanity.

A free-to-play, fast-paced multiplayer shooter that features player-controlled portals. It takes the FPS genre to a new dimension with portal mechanics, delivering high-flying, multi-dimensional combat. IGN describes Splitgate as “Halo meets Portal".