What about these mobs: chicken, pig, sheep, cow, jungle cat, cat, wolf, dog, bat, villager, zombie villager, squid, snow golem, iron golem?
Of all the mobs...
Most useful: the cow. From it, you can get steak for food, and leather for armor & books.
Most annoying: the enderman (followed closely by creeper), because of their ability to destroy my landscape.
Cutest: jungle cat kitten. (However, at one point my pick would have been skeleton. True story from when I first started playing minecraft: I dug a shallow shelter into the side of an extreme hill, closing off the entrance with blocks of glass and a dirt "door". Of course I had no bed, so had to wait out the night, watching zombies, skeletons, spiders, and creepers wander around just outside my shelter. As the sun started to rise the next morning it began raining and into view wanders a skeleton wearing a "yellow rain suit". Only some time later did I find out that it wasn't a rain suit; it was gold armor.)