Welcome to Night Vale (serialized podcast/radio sci-fi comedy), all 2015 episodes
All episodes written by Joseph Fink and Jeffrey Cranor, and produced by Commonplace Books.
Episode 59: Antiques (release date 1/1/2015)
Episode 60: Water Failure
Episode 61: BRINY DEPTHS
Episode 62: Hatchets
Episode 63: There is No Part 1: Part 2
Episode 64: WE MUST GIVE PRAISE
Episode 65: Voicemail
Episode 66: worms...
Episode 67: [Best Of?] (release date 5/1/2015)
Nominating this for long-form rather than selecting a single ep for short-form, because both Voicemail and [Best Of?] are already brilliant and it'd be difficult to choose between them. Also, it just makes sense (for me) as Night Vale is a sustained, ongoing body of work.
Note: The Night Vale live show "The Librarian" was first produced and released in 2014, so is not eligible as part of a 2015 release.
Night Vale wiki list of episodes: http://nightvale.wikia.com/wiki/List_of_Welcome_to_Night_Vale_Episodes