Batman: Future Imperfect
by PDebord 
When the Joker steals a series of seemingly defunct scientific devices, Batman can only puzzle over the mystery at first. The pieces finally come together when the Clown Prince of Crime obtains the emerald energies of the Green Lanterns, using it to search for a world without a Batman! And as the Caped Crusader follows after him, Batman instead finds himself in a future world too dark even for the Joker, with a grim and gritty Dark Knight of its own!