Sometimes it is the small touches, that add that bit of je ne sais quoi that makes the experience more enjoyable.
For example: I am living at RR for the first time. No MM, just me and Dogmeat. I am loving it. I placed a doghouse for dogmeat out under the canopy and dismissed him to RR so I could do some crafting and close the doors to RR without Dogmeat running around and opening them again. I am going about my business, and walking from the garage area around through the dining area into the back room, and what do I see? Dogmeat is just outside and is looking in through the window with his front paws on the window sill and whining a bit. Felt like a real dog. Gotta love this game!!
What are some things that surprised you and made you appreciate/experience immersion a little bit more?