Trivia: During the big fight between Batman and Superman, a broken window has the same shape as Ontario, in Canada. Superman creator Joel Shuster was born in Toronto. The broken window is only ever shown from Superman's angle, not Batman's. This was confirmed by Zack Snyder as being a deliberate, if obscure, easter egg.
Continuity mistake: After the mercenaries kill everyone in the desert, there are two guys looking at them using two monitors. The pencil below them changes from white to blue.
Continuity mistake: In the beginning, Bruce Wayne drives his car towards all the chaos, but the crowd is too thick for him and his car to get through, but with movie magic suddenly Bruce and his car are at the front of the crowd. (00:07:00)
Chosen answer: It is Flash. He is wearing armour because of whatever has transpired in the future. He often wears an armoured suit in dire circumstances in the comics.
Also, if you look at the bottom of the image frame you can just make out the Flash icon on his chest piece.