This dog and cat combo really annoy me. The dog is meant to be stupid and the cat cranky and cynical, but it's poorly done. There are a lot of more interesting anthropomorphic animals in the comics.
Runners-up: Hagar the Horrible, Mother Goose and Grimm, On the Fastrack, Prickly City
Yes, it's a poop joke, but it's a funny poop joke.
Runners-up: Agnes, Big Nate, Daddy's Home, Dilbert, Frazz, Lio, Pearls Before Swine, Pooch Cafe, Zits