Bubbline! That was probably the other one I was thinking of. Though I was reading some old Yuri on Ice posts the other day, on which I preserved someone else's tags that were contemporary with the giffed episode where Victor whistles at Yuri:

#ah i loved this #and i don’t really mind them not ending up together #most likely it’s just fan service #but i do enjoy the fan service to bits #but yeah i would love them together #not expecting or even really hoping #but would love it

So possibly Yuri on Ice counts as well, because people genuinely thought it wasn't going to happen!

The only one I know off the top of my head for books is the PJO verse, which I haven't actually read.