I'd love to say the barn owls are the cutest... and they are ADORABLE creatures... until they start their screeching. Christ! They are annoying when they get wound up! Still cute to look at, though.
Owned plenty of rats... had one give a litter. Ugly little pinkies until they get fur, and when they open their eyes, cuteness incarnate. Then they start moving, and you can never keep track of them. Kind of like human babies.
Ultimately, gotta go with kittens on this one.
Ancient relic of a by-gone era.