Returning to (...) (SPOILERS)
The chapter in which Isaac sets foot on the Ishimura again is probably my favourite gaming moment ever. I was pretty freaked out seeing those same corridors and rooms again, and they keep you in suspense by not sending any necromorphs your way until you're well into the ship. Those first minutes on the ship were pure genius in my opinion, the lighting(!), the eerie silence and absence of music, the design of the CEC sheets and tools covering that awful place you once knew so well. The game is a masterpiece, quite frankly.
"If I have one more piece of vomit pie, I'm gonna pumpkin.” - Roger.