This month Czech retro gaming site High-Voltage.cz ran a competition for DOS games, specifically MS-DOS 6.22 games in text mode that could be run on a 486DX / 50MHz with 8MB of RAM. Fortunately you can also play them on a more modern machine thanks to DOSBox.
The six entries can be downloaded from the link in the blue box on this page. They include a sci-fi shooter called Space Assault and a dungeon crawler called Dungeons of Noudar, but the overall winner was action platformer Silly Knight.
Silly Knight is about stabbing skeletons and bats (who follow the floaty trajectory bats are required by law to follow in games), while collecting keys to unlock doors. You have three hearts of health to see you through, and they refill when you pass a checkpoint by lighting a fire in a sconce. It's a hell of a thing for creator Petr "AfBu" Kratina to have squeezed into a 34KB zip file, and you can find at DOS Haven.
Good luck! You'll need it.