I LOOOOOOVE huddling together for warmth. I think because I hate cold weather, so it appeals on a very basic, creature-comfort level for me. There's just so many aspects of it that I adore: the H/C of usually starting with a blizzard or fever or falling in a river or being in an abandoned cabin and needing some way to keep warm, the awareness of each other's body outside of explicit sex (not that I am opposed to this trope ending up in sex! But there's usually at least few minutes of platonic cuddling first), the awkward self-awareness of being so close to another person, the fundamental pleasure of slowly warming up and having feeling return to fingers and toes... it's all just so lovely and comfortable and nice. Like a cup of hot chocolate!

Despite all that, I've never actually written it. I've got a couple of fics that take place during snowstorms or where characters mention being cold, but they all lack huddling, alas.