The old, infinite dungeon crawls from games of yesteryear were always fun.
So, when I heard about Roguelike Megadungeon, I was curious to try it out.
It's a super quick (15 minutes!) way of generating a dungeon on the fly.
Passages, doors/secret doors are made up by yourself.
I liked the process of having 36 d6 and checking the die results to the tables. Of course, you could make your own dungeon flavours up too.
Great for last minute game sessions or solo enthusiasts!