Definitely human babies. Cats make me sneeze and dogs bigger than a suitcase scare me. I hate big dogs, and big dogs have big-ish puppies.
Toddlers are the cutest. They're so funny. You can't teach a dog or a cat who the beatles are, only to have them say later that day that their favourite singer is "the ladybirds".
Now that, my friends, is cute.