I have or have had Rosie, Fauna, Diana, Merengue, and Kid Kat. I had to get rid of Kid Kat. Not a fan of jocks, or cats, and Rosie's on my list to leave right now, I find her a little overrated and she's overstayed her welcome. Merengue just moved in, I love her design, same with Fauna, but I have a lot of normals in my town (why are they all so cute?!) So, I guess that makes my favorite Diana. Who I got out of my campsite, and ended up loving. She's really pretty, and so is her house.
a lot of the tier ones are my favorites, because i'm boring and have a somewhat generic taste, but diana is my #1. her design and color scheme is gorgeous and her house is very appealing. not to mention i am a big fan of deer. all in all beautiful villager, will always recommend.
Kid Cat is the only current tier 1 villager I REALLY like, but if he ever moves down my favorite will be Fauna :-]
I've never had her but I have a few friends who do and she's lovely.