Tank! He lived in my town for about a month and I LOVED him then he moved away after I had a break in ACNL. I have also had Rhonda but didn't like her that much.
I really enjoy the rhino villagers. Tank is my favorite villager and was the first villager I ever met when I began playing AC, and Merengue is another one of my top 10 villagers. I really like Tiara from ACGC, too. Wish she returned in the WA update.
Merengue is my favorite. She's in my mom's town and I have had her a couple times in my old towns. She's so darn cute, but I do love the other rhinos too.