There's a tile with the emoticon sort of icon with a lot of notifications.
An early build of Cortana (Wishful thinking.), or just some app on the store I might have missed.?
I'm not sure what it is but it's not Cortana as she wont be an app, she'll be integrated into the OS. Rumor is she'll be on the search button instead of big search but if anything it'll be like how TellMe is now.
It's Cortana. Remember when the first reports came out and they said it looked like this...
I imagine it's expression will change as more notifications come in, similar to how the messages tile goes from smiley to wink to shocked. Sunglasses could be similar to shocked face.