[The Saucepan Man]

Seems a pretty good list to me Manardariel, but I would question one or two points:

Smaug isn´t in there, because for one thing he´s dead, for the other his presence never threatend the whole of ME. The dwarves and Dalemen were the only ones scared of him.

I understood the question to relate to the whole of the 3rd Age, so Smaug would figure in that. Also, he might only have been a problem for the Dwarves of Erebor and the Men of Dale as matters turned out, but had he survived, he might well have become part of the threat to the whole of ME. My understanding is that Sauron planned on trying to persuade Smaug to join his forces and that this is why Gandalf "arranged" the adventure told in The Hobbit.

Hobbits (as a unit)

If we start talking in terms of more than one individual, then many more possibilities open up. The armies of Gondor, the Riders of Rohan, the Orcs, the Easterlings etc etc. The list could become very long indeed!

I do think that yours is a very good list of the principal powers involved in the War of the Ring, although shouldn't Shelob figure in that one? Also, possibly, Faramir?