Carmen seems to be pretty well-liked in my town- she gets along well with just about everybody, Moose and Agnes both consider her their best friend, and O'Hare has a crush on her :3
Kid Cat is also popular in my town lately. Punchy admires him, and he seems to be having a fling with Felicity and Tangy, who are always mentioned hanging out with him.
Everyone talk of everyone in my town, but that depends who characters it is. Fauna talks abaut Erik, Whitney about Apollo, Tammy about Rosie, Drago about everybody, Hamlet about Marshal and Marina about everybody too.
Blaire is the one that the is sent the most presents (@ my villagers I'm proud), but Marshal seems to be the most talked about. Filbert even said once that he heard Marshal has really ticklish feet.
I don't necessarily have one particular popular villager, but Stitches and Shep are pretty much best friends. They're constantly at each other's houses, asking me to bring one to the other's house, and other villagers mention their friendship pretty consistently.
It's pretty adorable.