5. Quincy Sharp
We promised that some of these theories were crazy, and this one is real loony bin territory (are we still allowed to say that?). The former warden of Arkham Asylum and former Mayor of Gotham Quincy Sharp has been pegged as a possible suspect for the Arkham Knight. Though he certainly doesn't match the Knights physical description, he does have valid motive (in his own mind) for targeting Batman and destroying Gotham city. Sharp is a schizophrenic who believed himself to be the spirit of Amadeus Arkham (the Asylum's founder) and actually spent much of the first game murdering many of the Asylum's inmates in the name of permanently curing their criminal insanity. Through the fascinating Chronicles of Arkham side mission, Batman discovers that Sharp planned on murdering many of his rogues' gallery and even attempted to kill the Joker. Sharp somehow manages to escape Arkham Island by the end of the game, but not before leaving a final message for Batman to carry on his work. In the second game, newly elected Mayor Sharp is responsible for the opening of the titular Arkham City and is actually being manipulated by Hugo Strange and Ra's al Ghul as part of their Protocol 10 plan to destroy the evil citizens of Gotham. Once Sharp has served his purpose he is then outed for his corruption and heinous atrocities and imprisoned within the City where he would have presumably been killed immediately had Batman not interfered. Now one year later, having lost his office as Mayor, his respected reputation and his beloved asylum, it is possible that Sharp may have fully succumbed to his split personality as the Spirit of Arkham and set his sights on Batman, for failing to protect Gotham City. It's crazy alright. But we're only getting started with the crazy theories.