My three favorites are, (in exactly this order) Alex, Mia and Piers/Picard. I love their character, design, simply everything, they're just perfect to me (and I loooooooove blue/teal hair). x3
Other characters I like: Felix, Jenna, Sheba, Ivan, Saturos, Menardi... oh, I guess it's better to start with the charas I hate - but that's not the question here xDDD