Right now, my favorite cat is Tom. Partly because he's in my town and partly because his coat pattern and crankiness reminds me of my cat.
Punchy is adorable too. If I ever got him in a town, I don't know if I'd be able to let him go, despite having had him already and wanting to experience new villagers.
Hmm, can't seem to make up my mind. I'll pick Rosie for nostalgia sake, she was my first villager in the GC game... I like Tabby a whole lot too. Unfortunately I don't particularly like the peppy personality in NL so I don't think I'll be getting either of them for my town.
I'm not a huge fan of the cats. I currently have Lolly, although I do find her a little boring. I had Rosie in a different town, but auctioned her off because I couldn't keep her - I liked her more than Lolly.