Maybe it'd sound odd to a lot, but I think Ithor is a nice one. Merely because of the protection it is given by the Ithorians to the extent where they seldom even go to the surface, if at all. I love the whole idea of a planet kept as healthy as possible by its inhabitants.
Nar'Shadaa is also pretty cool.
"Neither dark nor light, but both all the same.
Neither hero nor villain, but both all the same.
Neither balanced nor chaotic, but both all the same.
Neither alive nor dead, but both all the same."