What is your favourite old school game?

I'm sure most of us here would have been gaming for quite a long time, years or even decades. I got into gaming as a kid back in the '80s, and have played many types of games but some are timeless and more memorable than others. For me, the very old but innovative adventure/RPG hybrid Quest for Glory I: So You Want to be a Hero is one of the definitive hits, and perhaps one of the earliest sandbox, open world and survival games of the time, something that Ultima VII: The Black Gate would surpass several years later.

For instance, you could pick up pebbles from the ground and use it as a tool or weapon, obtain empty flasks and fill it with water or alchemy concoctions. You had to eat, drink and sleep on a regular basis or risk starvation or exhaustion and eventually death. You had to find a safe place to sleep or you would never wake up due to being killed by monsters in the wild while you slept. There was a day and night cycle that progressively got brighter or darker depending on time of day, and if you wanted to spend the night in the town's inn you had to make sure you were inside the town walls as it would be shut and locked after nightfall. Though, if you played the Thief character, you could climb the walls and get in after dark. There were NPCs like the tavern ogre that would beat you up and throw you out the door if you annoyed it by talking to it too much, or the mysterious rogue that loiters at the town entrance who could throw multiple daggers at you and kill you before you could if you so much as tried to throw a dagger at him. The game had a lighthearted yet hilarious sense of humour, and it had a lot of cultural references that were rather clever, and other times just make you go "Huh... what the..." and laugh out loud.

Sure, the game is well over 20 years old but in my mind it is one of the finest examples of video gaming. So, the question for discussion that I would like to leave open is: What is your favourite old school game?