Cube was my favourite villager when I first played the original AC. He stayed my favourite for a long long time, but I think he's been displaced by Roald this year. (who moved into both my WW and NL towns. ^_^)
Friga has always been high on my list too. Had her for atleast a year in every game except NL.
Boomer, hands (flippers?) down. My daughter loves him, too. I had him in my first town but sadly I had to reset (hated my house placement) and lost him.
I think Aurora and Sprinkle are my favorite! And River, you can reserve Boomer from me if you'd like. As soon as I get his picture and as soon as he asks to move, I'm going to put him on the Villager Trading Board!
Cube, although I'm still trying to figure out why the AC Wiki says he isn't actually an animal villager. Is he a stuffed animal like Stitches or something because if so, I never even noticed?