Death of Zoom
Barry had plenty of justification to kill Zoom, but instead he allowed Zoom to be consumed by the very creatures that had been hunting him all along. In a moment that felt very akin to something out of Batman Begins, Barry chose not to kill his foe, but chose not to save him from his death either.
But what seems to be one of the coolest nods is that at the moment of his death, Zoom looks suspiciously almost exactly like the time wraith that tried to kill Barry earlier in this season.
