File this one under completely unexpected. Doom has been used to create many things, but never would one assume a Batman game would be amongst them. Equipped with bat-a-rangs, smoke bombs, and a slew of other bat-gadgets, the Dark Knight squares off against Gotham thugs and a rogues gallery of Killer Croc, Bane, Penguin, Scarecrow, Two Face, and The Joker. Batman Doom was created by ACE Team Software in April of ’99, completely converting Doom 2’s source code to include Batman sprites and revamped environments to look like Gotham City, the Batcave, and Arkham Asylum. Batman Doom is the most complex mod for Doom II.