Any Altmer other than those Radient Raiment lasses. Why did they have to make those the only ones you can marry? It severely limits your options to... well, two people. Actually I think you can only marry one of them. Maybe one of these days I'll make a submissive-type character. I'm sure he'll enjoy her company.
And Serana. What is it with her? I go through all of the trouble of making her turn into a human, kill her own father and his friends, and force her to talk to vampire hunters... What's not to love? Seriously though, I don't know what Bethesda's thinking behind this was.
Then you have that Nord in Solsteim, Frea. I rescued her village and saved Solsteim! I think I deserve some "lovers comfort" for the effort.