Huey and Elmer. According to Huey, Elmer's the only human being that he saw as something beyond "experimental guinea pig," and Elmer's been noted to be one of the only men in the world not thoroughly creeped the fuck out by Huey. Also, while most men compare beautiful women to angels, Elmer compares beautiful women to Huey.
Elmer: I could've sworn that Huey was the only one on that boat who was this pretty...
The relationship just becomes more and more suspect as more of their backstory comes into the clear (Elmer, for example, seemed to have a tendency to make bets with himself to see if he could make Huey smile within a certain time period). And some of the quotes from Huey, such as the ones below, make him seem very Tsundere towards Elmer.
In the 'What do you think about Elmer C.Albatross' section of the novel, Huey said this in 1705, 'An annoying person. That nosy personality of his will just cause problems. I'm looking forward to when he dies.' but in 2002 he seems to have warmed up to him more and says,'He is...a close friend. Simply a close friend. No less than that, no more than that. Though it would be too embarrassing to tell him something like that.'
Ladd Russo and Claire Stanfield (Vino) have been given canon (yes, canon) material, aka, they got married, in a DS game.