That’s a toughun… Hm. I think my favorite one is a tie between Tom’s from Zombie Exodus and Finch from A Study in Steampunk.
Tom’s really stuck with me for some reason, and no, I’m not talking about what we know happens later on. There’s just something about the way the interaction between the player and Tom goes (during the scene itself) that left a lasting impression on me. Plus… that scene on the couch was hot, not gonna lie. The bit where the MC’s looking down at Tom and realizing that, at that moment, he was theirs? A+. 
On the other hand, Finch’s scene was very emotional and visceral and it actually breached the fact that emotions were involved and grew. Too many romance scenes just have the MC and the RO kiss and… that’s it, but Finch’s scene was this declaration that was touching and continuously kept coming up. It was satisfying and it was beautifully handled and executed. 