Froakie is the coolest.
I keep watching the video looking for clues or hints in the battle scenes. All three of the starters used second attacks that didn't seem to be of their primary type, possibly hinting at dual types later in their evolutions. I think Chespin used Night Slash so I might become a Grass/Dark type, took a closer look at the second attack Fennekin used and to me it actually looked like it was beginning to launch a Dark Pulse attack judging by the dark purple circles coming from it's mouth, so now I think it might become a Fire/Dark type, and Froakie might evolve into a Water/Fighting because it used what could have been Close Combat. I also think Froakie's second attack could have been Acrobatics, and it's design could hint at a possible Water/Flying type judging from the cloud cape around it's neck. Hopefully Flying is the case because I think a flying frog would be a good addition to the fighting frog Poliwrath, poison frog Toxicroak, and ground frog Seismitoad.
So far I'm mostly going with Froakie, but I have to see the complete evos to know for sure. All three look interesting in their own ways so my final choice could be any of the three.