Aside from all of them, I have a short list in no particular order or preference.
Wizard - Depending on how multiclassing works and training feats, I'd like to see how I can add some clerical flavor to the Wizard like my old favourite Mystic Theurge character.
Warlock - i'd like to do a Fey pact Eladrin myself, though it seems that everyone wants to do that character. Just to be different, I might go Star pact Tiefling.
Rogue - I like the sound of the new sneak attack rules and I like the image of a suave, lightly armoured, swashbuckler who attacks with precision and deals alot of damage. Oh, and from the sounds of things, this might be a great class to play solo what with healing being spread around a bit.