As for canon, I'm partial to Anything Nepeta + Dave + Karkat + Jade (any combination of any of those four, or hell, all four at once lol), I think they all have a lot of neat dynamics and it's overall pretty cute.

But one of my favorite unusual pairs I've ever read about in the fanspace that made a really good point is a young adult Dave <> Cronus. In the story it's from, trolls lived on earth, but were sort of an oppressed people. Cronus was very self destructive and, frankly, an asshole, and Dave was forced to keep an eye on him. Eventually though, it became a thing where Dave was needing to protect this broken troll from endangering themselves, while Cronus realized Dave started seeing him for who he really was, and felt the need to start getting better for him, it was pretty sweet and honestly again, one of the strangest pairs I've ever heard of.