It was OTP* at first sight. When Tormund saw Brienne and we saw Tormund see Brienne, it felt like time slowed down. No two characters need a romance more badly than these two warriors. They both have had a rough time. Brienne fought a bear. Tormund had (what we imagine was) a tumultuous, short-lived fling with a bear.
*OTP = one true pairing
If you've only seen the show, this pairing is super disturbing considering that the Hound threatens Sansa and later tells Arya he should have raped her. In the book, however, their relationship is more developed, leading many fans to ship this unlikely duo. They're different in every way. Sansa is gentle, Sandor is cruel. Sansa is alive, Sandor is "dead." But hey, opposites attract, right?
"Sansaery" is perhaps the most popular ship in the Game of Thrones fandom and definitely the most beautiful. While they might be an unorthodox pairing, they've got a lot to bond over, like how it feels to be married to a sadist.
Remember before the Briemund era? Fans loved to ship these two knights, and it made sense: they're both loyal and strong and blonde. And Jaime jumped into a bear pit to save Brienne. Did your significant other fight a bear for YOU? That's what I thought. It's too bad Brienne wasn't born in the Lannister family, then Jaime would be all over her.
This ship sailed before the HBO series even began. The official Westeros story is that Rhaegar kidnapped Lyanna from King's Landing, but some believe that Lyanna and Rhaegar fell in love and ran away together, making them the series' oldest OTP since they died long before the start of the books.