The 90s were an amazing period for innovation in video games. You have heard of such legends in the FPS genre, like Wolfenstein 3D, Doom and Duke Nukem 3D.
An amazing game you may not have heard about is Exhumed, or Powerslave, depending on the region you were inhabiting at that time. The game runs on Lobotomy's proprietary SlaveDriver engine, which has full 3D capabilities. At first glance, the game is the usual deal: labyrinthine levels filled to the brim with monsters, weapons and keycards, but as you go along you will notice an almost metroidvania structure, because you are able to go back to previous levels and use newly acquired powers, like flying or walking on lava, to discover new paths which were previously out of reach. Tying into the exploration aspect of the game is the ending which changes based on your actions,which was not very common outside of the RPG genre. In order to get the best ending, you have to find all 8 radio transmissions that are scattered throughout the levels, a task that is made easier by the fact that the levels containing them emit a beeping noise while you are in the overworld screen.
Another cool feature of the game is actually a minigame called Death Tank, which was unlocked by finding 23 dolls representing the dev team which are also scattered all over the place.
After the moderate success of Powerslave, Lobotomy went on to handle the Saturn versions of Quake and Duke Nukem 3D. Quake was a huge technical achievement, because the game in its original form, using the id tech engine was impossible to run on the messy hardware of the Saturn, so, unbelievably, Lobotomy recreated the game from scratch on SlaveDriver. Levels were cut out, the multiplayer was not even attempted, but they actually managed to tackle this monumental task.
Duke Nukem received the same treatment as Quake, aka the remaking from scratch, but it received its multiplayer modes, like dukematch, and also a new version of Death Tank, called Death Tank Zwei, which was unlocked by having a savegame from a previous Lobotomy title on your system or, in Duke fashion, destroying all the toilets in the game.
After releasing these 3 games on an underperforming platform purely out of love for it, Lobotomy Software went under. Their feats may have been burried by history, but this marvelous husk of a once perplexing developer was finally Exhumed.
As a side note, you can download an unofficial PC port of Powerslave, called Powerslave Ex, and I encourage you to do it, because it is a damn good game.
