I always liked Saturn, cause it was big and had a ring thingie.
Neptune sounds nice and it's blue.
But I think it's Mars. Love the name, and it's not that far away that we cannot colonise it within 100 or so years.
If talking about fictional planets, then maybe Mira from Xenoblade X. Lovely places to explore, though most things will kill you, so not that safe. Would say something about Metroid planets, but they very dangerous, too.