Doom

Doom was released in 1993 by id Software with John Carmack and John Romero at the helm. Its cultural impact was such that it is largely considered one of the most influential games of the 90s, both for its controversial approach and for how fun and innovative it was for the time.

In this game, you play as a Marine on a base on the moon. A portal to the underworld seems to have opened, and your task is none other than to stay alive by killing demons, possessed soldiers, and supernatural creatures on a journey through the underworld itself.

The shareware version of the game that was distributed at the time allows you to play each of the nine levels that make up the game's first episode. Although it's currently impossible to play this game directly on modern computers, there are interpreters that allow you to do so on even the most modern PCs, as well as the addition of new features, such as free aim controlled by the mouse and overall improvements to the graphics.