Yeah, Deja Q is just a wonderful combination of actors & characters with Spiner & DeLance. Starship Mine has a jewel in it to with that small talk scene, for sure. I'm sentimental. I thought Data & Spock had some memorable exchanges in Unification.
I'm not sure how other people feel about it, but "In Theory" is a pretty brilliant character study for him. He is also one of the more enjoyable parts of Time's Arrow
Honestly though, nothing amazes me more, with that character, than when he shows his truly emotionless nature, to its fullest effect. The two examples which stand out are how he manages to slam the ice door, on his abductor, at the end of The Most Toys, by essentially telling the guy that he had no feelings at all, about everything he valued being taken away from him
But nothing, I mean nothing, will ever be as icy cold as when he shut down that crazy lady at the end of Silicon Avatar. After how that lady had projected all her feelings about her son onto Data, what he said to her would probably have driven her insane, or made her suicidal, & he did it with all the coldness of it being any other equation he might have to consider
They were pretty careful about how often they had him do something like that, but boy they were great both times. lol though I suppose buring down the community's aquaduct, in "Ensigns of Command" could've seem rather cold to, but not really