I guess it falls to me to fill this up.

In Memoriam, a reimaging of Toaru Majutsu no Index that generally raises the competence of everyone involved. Significant changes; prior knowledge not required.

Overlady, Zero no Tsukaima as seen through the lens of the Overlord games. Guess who's the new Overlady. Prior knowledge of ZnT definitely required; prior knowledge of Overlord positive but not required.

Halkeginia Online: Sword Art Online meets Zero no Tsukaima meets Island on the Sea of Time. In short, Louise summons Alfheim, as it turns out that AGI beats magic but AGI has odd priorities. Prior knowledge of ZnT and SAO required. Warning: TVTropes link.

Uchibi Sasuke: Naruto crackfic-with-plot. Highly amusing. Prior knowledge preferred, but fic is not to be taken seriously.

Game Theory: Magical Girl Lyrical Nanoha, with a slightly saner and far more rational Precia Testarossa. Highly recommended, prior knowledge of Nanoha preferred but not required; it's a rewrite. Complete, sequel in progress.