If you're unsure about which Anime are included in Summer 2015, just go check out AniChart (Note that the Anime such as One Piece or any long series that started airing long ago are not included.)
Anyway, just like the title says, which is your favorite Anime of this season? And why do you think so?
In my opinion, its Rokka no Yuusha because of its unique premise. There's plenty of flaws in it such a character development, but I still think it deserves more attention than what it is getting. I might be a bit biased on this, since I've been waiting for months for the Anime of Rokka no Yuusha to be released, but meh, its still an anime I might give 10/10 this season.