Thinking about doing a roguelike map, made of isolated geometry linked by randomized portals.
You'd make a bunch of unconnected rooms and corridors, some could be identical or slight variations, some could be unique.
In each room, you'd create a few interactive portal lines, with no target. Behind them, create some "dead end" geometry. Portal lines get a "room number" in a custom UDMF field.
Each portal line would belong to one of a small number of "portal styles." All portal lines and the sectors next to them in one "style" would have identical line length and sector height, and maybe similar floor texture, light levels, etc.. Portal lines get a custom UDMF "style number."
When the level loads, an ACS script runs and does a sort of loose
Wang tiles thing to link everything together -- basically pick a random room, link each of its portal lines to another portal with the same style from another room, rinse and repeat.
Ideally you'd have enough rooms in the map that many of them wouldn't show up in a reasonably-sized dungeon, so a unique room would only have a small chance to appear on any given run.
EDIT: Just tried this out, works surprisingly well. This could be interesting for a map collab...