There will be spoilers for the game and the DLC in my text and the comments
If you don’t want to be spoiled, play the game first, it’s a really really nice game that’s best when discovered
My favourite moment for the game (as for most players), was when I fetched the Warp Core and had to go to the Nomai Ship. The music made my heart beat so much, and the trip seemed so friggin long.
But my best discovery within the game is understanding how simply turning off the flashlight would be enough to make the quantum objects move. It was so satisfying discovering it for the first time.
Quantum moon spoilers
One of my favourite discoveries was the multi-layered puzzle that is the Quantum Moon. At first I was super puzzled by why I couldn’t seem to land on it, but after getting the clue to take a picture of it (from Giant’s Deep, I think?), actually being able to land on it was a fantastic feeling.
From there, I found the tower and immediately tried getting to the eye, but was met by the solid wall, and that stopped my progress. I explored more of the solar system, and I remember always being confused on how to climb the tower in Brittle Hollow. One loop, I thought to myself, “hey, maybe I should wait here until it falls into the black hole.” The piece fell through after quite some time, and I was able to float into the top section, which I believe reveals that you need to venture to the north of the Quantum Moon to explore the sixth location.
With this knowledge gained, I restarted the loop, went back to the Quantum Moon, utilised the tower to make my way north, and the excitement I felt when I managed to open the door to the sixth location unimpeded was immense.
Just so many things coming together for that one moment, amazing.
I think it’s one of the best puzzles I’ve ever seen in video games, that along with the main puzzle of the game. It’s so nice the developers added the Quantum moon plot, when it’s not even necessary to finish the game