If my estimation of a microgame is measured by the number of copies I possess, then Deathmaze sits atop my microgames list.
I own two copies of Melee, Wizard and Death Tests 1 and 2. I also own two copies of Starfire. But I own three copies of Deathmaze.
Deathmaze was designed by Greg Costikyan, and was published by SPI in 1980. Deathmaze truly is rules-light, eclipsing even Melee and Wizard in that regard.
The character record sheet for Deathmaze can fit on a playing card, and consists of the following information:
Class (Hero, Thief or Wizard)
That's right. No character stats whatsoever. Part of the beauty of the game is that you can create your character and be ready to play in 5 minutes. And the game is designed for solo play, meaning their is no prep time necessary for a game-master, assuming there is one.