Hmmmm, depending on the genre, in this order going by D&D standards.
High fantasy: Dragon-red. I love dragons, when I was little they weren't just big fire breathing lizards they were a symbol of power and possibility, magic powers, enormous strength, the ability to fly, infinite beauty,super sense, they were my childhood super man I devoured everything that related to them. Dragons are the ultimate plateau in my book. Red because they look the coolest and were the freest ones of them all doing whatever the hell they pleased with no one capable of telling them not to.
Steam punk/scifi: Warforged. If I didn't feel tired... I feel tired all the time now and there's a lot of times I wish I had the power to never feel fatigued.
Grimdark/horror: Demon, Incubus. Again super powered magical being, but the real pull here is that they commonly have the ability to slip between dimensions resulting in a form of teleportation combine this with their shape changing prospect and you've got yourself a winner. Freedom's big for me, I love that and nothing say's free to do whatever like the power to be anyone you want anywhere you want.
Low fantasy: I don't really prefer any of the creatures in low fantasy over human but I guess if I had to choose I'd say Ogre OR giant. After all if you have to be an ugly muscle monster why not be one of the strongest?