The passage I chose is near the beginning of the story, in the last paragraph of chapter three.
"That photograph was taken on the last day of our fatal summer and just a few minutes before we made our second and final attempt to thwart fate. Under the flimsiest of pretexts (this was our very last chance, and nothing really mattered) we escaped from the café to the beach, and found a desolate stretch of sand, and there, in the violet shadow of some red rocks forming a kind of cave, had a brief session of avid caresses, with somebody's lost pair of sun-glasses for only witness. I was on my knees, and on the point of possessing my darling, when two bearded bathers, the old man of the sea and his brother, came out of the sea with exclamations of ribald encouragement, and four months later she died of typhus in Corfu."
I thought this passage stood out when I was reading it for the first time. Especially the last sentence. To me it's very vivid and it has great imagery. In a "violet shadow" with "red rocks", and only some lost sunglasses looking on. It seems like the colors are the colors one would see looking through sunglasses. It makes it seem sort of surreal. The whole thing makes it seem so sad and beautiful; it's the lovers only chance to "thwart fate". And then the old men come out of the water completely ruining the mood. I loved the Hemingway allusion to the "old man of the sea" and the tacked on "and his brother". I could completely picture the scene and every detail of these two old men laughing and being crude, encouraging the young couple. I think I may have even laughed out loud when I first read this. But then all of a sudden, "four months later she died of typhus in Corfu", just like that. He just segues into this sad piece of information, with no fancy prose or anything. He just says it, and that's the end of the chapter. It's all a somewhat unexpected way to tell the readers of this tragedy, but in way it makes it seem more drastic. Humbert doesn't try to sugarcoat the news because it was such a terrible thing that happened to him, he really was affected by it, so much so that he couldn't even come up with the fancy prose to talk about it. That's how I took it at least. And I just love the way Nabokov can make you laugh with joy and then sit in stunned silence in only one sentence. He truly is genius.