My favorite villager has been Grizzly ever since I played the original Animal Crossing on the GameCube. My second favorite is Anicotti. Both of them were starters in my first ever town and I've considered them my best friends ever since.
Mine's Marshal!! And I have him in my town (until god knows how long tbh cuz I am not consistent with this game and he'll probably move out, frick me). He's soooo cute though and I love his smug personality and he's a sweetheart as well.
Definitely Coco. Ever since my childhood she's been my favorite villager. For me, she's the perfect balance of eerie, cute, and a little mysterious- I just can't resist that amalgamation of traits. In every game, she has always been my best friend, and I doubt that'll ever change.
Either Apple, Zucker or Felyne. I haven't been able to decide on just one favorite villager, though I lean more towards Zucker. Both his takoyaki look and laid back personality appeal to me.
Olivia. She was one of the villagers that came to greet my character in the very first town I created in New Leaf and she immediately became my favourite. The day she moved out because I took a month-long break for NaNoWriMo one year and she packed up and left without me being around to stop her, I was so heartbroken that I deleted that town and started over. Mind you, this was years before the welcome amiibo update, and since I was relatively new to AC, I didn't know about the 16 villagers cycle.