I would have to pick cats. I was very frightened by a stray dog when I was a small child and have never gotten comfortable with them, with the exception of a Pomeranian that one of my Mom's boyfriends had when I was a kid. That little poochie was sooo cute and I loved taking it on walks!
My cats have been very intelligent. I adopted one as a 5 year old and the other two as 6 month old kittens. The eldest, called Cupid, comes when I call him, "talks" to me when I come home from school or work, adores being picked up and held, likes to snuggle, greets EVERYONE at the door and likes to be near me whenever I'm home. In fact, he's sleeping in his usual spot near my computer as I type! I speak to all 3 of them as if they were human children and they respond to me.
My cats aren't much for doing "tricks" on demand, but they know when they're being scolded, praised or called to their human owners. That being said, I did some training with them when I first got them, so that they associate good behavior with things like being petted or catnip.