When it comes to Starters? I would say Oshawott. I am seriously in love with this Pokemon. It is just so adorable X3
As for others, I have also taken a liking to Blitzle/Zeburaika and Braviary. Whenever I do get the game, I'll know for sure which ones I'll like more than others. I find it interesting that you can only use the Pokemon for this generation, so we'll see.