Aria Montgomery. I'm 99.9% sure. I don't think she's the 'A' that will supposedly be revealed in the season five finale two weeks from now, but she definitely is 'A'. This will probably be a plot twist at the very end, in the series finale, at least I hope it will. My dream ending for Pretty Little Liars consists of Aria being 'A' – of her outsmarting everyone else and winning. I want the villain to win for a change. I want her to turn out to be a full-blown psychopath. And I think there's a pretty good chance of this happening because of a certain scene in 4x19 (gif bellow). I remember watching it and thinking how cryptic and out of place it was. Sure, at that time they wanted us to believe that Ezra was 'A', so one might think this scene was just another 'hey-look-Ezra-is-so-shady' scene, but if you were to rewatch 4x19 right now, you'd realize that this particular scene is in no way connected to the now-former plot. It was just sort of... there. Which got me thinking – what if this was foreshadowing? I don't think this was a random scene. I mean, this is Pretty Little Liars we're talking about, they don't do random. My guess is, Aria will turn out to be 'A' (she probably has DID and the more dominant personality, the 'A' personality, will somehow, in some way, take over for good), the other three liars will find out about this (I also have a theory Alison will die for real at some point), they'll take her down (either put her away at Radley or it will appear as though she died), and everything will go back to normal... or so they'll think. A few weeks will pass, they'll be happy, and then – boom. They'll receive a final message from 'A'. Right after that, in the very last scene of the show, we'll see Aria in a car, driving off into the night, wearing a black hoodie and a crazy, sadistic, smile. Ezra may or may not be in the car with her because – let's face it, he'd do anything for her. Plus, how cool would it be if these two were the 'A' team all along? So, yep... that's my theory... or hope, if you will. And yes, I'm well aware I drifted a lot from your initial question – oops. Sorry. But I felt the need to share all this.