Nick being the third wheel and Gatsby and Daisy's reunion. There's a long drawn out awkward silence where the two don't know what to say to each other, and Nick tries to encourage conversation with the duo. When Nick tries to excuse himself, Gatsby desperately tries to keep him in the room.
On the way from the Buchanan mansion to town:
Tom: I've made a small investigation of (Gatsby). I could have gone deeper if I'd known-
Jordan: Do you mean you've been to a medium? (laughs with Nick)
In both the book and 2013 film, this conversation between Daisy and Nick (at least in the film - the book is ambiguous about who replied to Daisy) at the Plaza Hotel:
Daisy: Open another window.
Nick: There aren't any more.
Daisy: Then telephone for an axe.
From the 2000 TV movie scene leading up to Daisy's and Gatsby's reunion:
Daisy (walking into the house): Oh! Flowers! Are we having a funeral?
Daisy (upon hearing Gatsby knocking on the door): And that must be the corpse!