A couple of friends (Nik Pantis and Jaris Renner) and I, after playing a little too much Hollow Knight, had the idea of trying to make a Metroidvania.
We got a core character controller working, along with a very easily balanced stats and leveling system, basic branching dialogue system, and simple interactables (for doors, etc).
The Player's balance settings existed as scriptable objects, so you could have and test different balance profiles and a custom editor which allowed you to manage the different stats using tables or curves.
The branching dialogue system had a custom editor and we had an event system tied to our dialogue system which allowed for us to trigger game events directly based on dialogue outcomes.
I also got to play with setting up audio reverb zones as a simplistic way to manipulate sound effects in different parts of the level.
I started playing with the animation system and put a system together where I could override some animation clips based on equipped abilities.
The project ended up getting dropped as all of us ended up too busy with other commitments, but it made for some great editor tools and exploration of what was possible with the engine.