I'm surprised I hadn't heard of this one before! A few developers have been building Nazi Zombies: Portable, a Call of Duty: Zombies demake powered by various enhanced forks of the Quake engine.
“A few developers have been building Nazi Zombies: Portable, a Call of Duty: Zombies demake powered by various enhanced forks of the Quake engine.”
If you’re adventurous, Sker Ritual and Hellbreach Vegas both apparently have good ProtonDB results. (Indie imitation games)