Definitely cats. I love cats and I think there are plenty of cats with good designs in the game. Also, I especially like Bob, so he's a must for any town of mine :p
I like Steep Hill and Go K.K. Rider!
Steep Hill is just because I like how it sounds, but Go K.K. Rider! is because it was the first K.K. song I can remember hearing (and I like how it sounds)