Shiki/Mikiya, Artoria/Shirou/Rin OT3, Archer/Rin (if distinguished from the former, I'd have said OT4 but...).
Gilgamesh/Enkidu. Gilgamesh/Saber, but only how I want it.
More... or less in that order? I think that pans out like a top four or five depending how it's parsed.