Aww, same! Tutu was in my first town and she was lovely!
I now have Wendy as my peppy. Honestly, she behaves like a normal so you wouldn't even know she's a peppy other than the things that she say, lol. But I think she's downright adorable with her watermelon scarf. Her furniture is also adorable - lots of fruit furniture.
I can't pick just one since I have a few favorites
Bella is my current peppy and she's SO cute. I love her weird face and her metalhead theme. Dotty and Ruby because they are cute/odd looking bunnies and I used to have Dotty in my first ACNL town. I have to include Epona as well if only because OOT was my first Zelda, and I kinda flipped when i realized she was in the WA update.