Quake is a famous fps released in 1996. In a preview section of Commander Keen (dated 1/23/90), we can see that originally the game was going to be a 2d role-playing game. Also, when in the mid 90’s they created the quake engine, the early testing was made on some Doom levels.
Also, as we can read on Wikipedia, the earliest information released described Quake as focusing on a Thor-like character who wields a giant hammer, and is able to knock away enemies by throwing the hammer (complete with real-time inverse kinematics). At the start, the levels were supposed to be designed in an Aztec style, but the choice was dropped some months into the project. Early screenshots then showed medieval environments and dragons. The plan was for the game to have more RPG-style elements.
Eventually, the whole id team began to think that the original concept may not have been as wise a choice as they first believed. Thus, the final game was very stripped down from its original intentions, and instead featured gameplay similar to Doom and its sequel, although levels and enemies were closer to medieval RPG style rather than science-fiction.
Before the release of the game or the demo of the game, id software released QTest on February 24, 1996. It was described as a technology demo and was limited to three multiplayer maps. There was no single player support and some of the gameplay and graphics were unfinished or different from their final versions.
As noted by Portend (check the video below):
There are quite a few differences in this deathmatch test release like the map designs and weapon models for instance. When I start moving and going down the stairs you’ll see armour in front of a gate, in the full release of Quake that armour is behind the gate.
After I go through the portal and across the moving platform, then back again… dropping down the lift is the Rocket Launcher (the red model which isn’t the finished version of the weapon). That hall in the final version has an alcove with the rocket launcher in it and straight ahead towards the steps is another alcove with the Quad Damage modifier sitting up top along with some boxes of health, that area as you can see doesn’t exist.
Some more info can be read thanks to old interviews with John Romero:
Quake as it turned out is not what Quake was supposed to be in either that original prototype (TFFJ) or in the original concept of what Quake1 was going to be. The idea completely changed and the only reason we didn’t change the name of the game is because everyone in the world already knew what we were working on.
Nope. Quake was one original idea that got changed 7 months before shipping to something totally different and the name remained because the world already knew what the game was called.
Our dragon was going to be a massive fly-by that traveled along a path outside the level, dropping in for some firebreathing every now and then. Mostly it was gonna be for a cool, huge character event. The Vomitus was going to be something disgusting that vomited small versions of itself that attacked you.
Thanks to Nathan for the contribution!