Ok so forever forever I've pretty much shipped Fluttershy with a deer boy and just recently did I actually design and name him. I did this basically because all other ships aren't good for Fluttershy and also here's why this one is the best and also my deercanon
So deer in the MLP world mostly live in the woods but have more of a spirit of the woods feel then like being elves or ewoks. But They also interact with the outside world so it's not a total isolation, it can be anywhere from deer who only live in woodland villages and ascribe to a completely natural lifestyle, to those who live on the outskirts of the woods, to even those who live entirely outside of them but are like good lumberjacks and are good at respecting the woods and stuff.
Ok so They don't have cutie marks -per say- but they interpret the whire spots on their flanks in sort of a tea-leaves future telling fashion. They often times have to do with like trees and plants and streams but not all the time. Willows was about either bunnies or critters I haven't decided yet, I sort of want to make his destiny rabbit-exclusive so he can have a higher level of knowledge on them then FS but her broader knowledge of creatures surpasses his and they learn from in each other that way.
But lets move onto temperment. Deer are shy but not in a paranoid nonsensical way, they're shy in a smart protective way. The dangers they face in the woods are very real and so they have reason to always be on their toes. Willow is timid and shy but not in a dopey way, therefore he matches well with FS on a same-same easy to see surface level, but he is actually very strong and decisive which helps to lead her without it being an overpowering image.
Big Mac's a good guy but he's a farm boy and if FS marries him young she'd just be raising 4 foals on the farm and would, idk I guess get to take care of sheep. But with deerboy here they can venture off into the woods and go on hikes and adventures but it's all very natural and forest based and pretty
So this is my essay on why all of your ships are now dead because deer boy wins fluttershys heart forever. Thank you for your time.