I go for the various species of bacteria and virii.
Why?
1. Ability to live in the most extreme environmental conditions, i.e. volcanoes, outer space, deep sea, deep earth, deep ice.
2. Ability to adapt and evolve more quickly than other animals.
3. Self contained, robust.
4. They have been around billions of years before any other animals, and are still around today.
5. Humans rely on the good ones for our very survival, and fear the most dangerous ones.
6. All animals probably evolved from them, which of course makes us the ultimate microbe thus far.
7. They are by far the most widespread and successful, population wise, of animal species.
8. They use all humans as a comfy hotel.
So, as far as unconscious intelligence goes, they blitz.
Please feel free to add to this list of microbe advantages, I'm sure there are many more.
Cheers.