If you liked
Ichiban Ushiro no Daimaou
|
...then you might like
High School DxD New
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Both are fan serviced filled harem anime's that involve judo-christian inspired lore such as demons and angels. This actually turns out to be really entertaining not just because of the fan service, but because of the lore, as well with the powers the both perverted protagonists obtain.
If you liked
Koukaku Kidoutai
|
...then you might like
Ergo Proxy
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Both take place in intriguing futuristic worlds that have a lot of secrets behind them. Along with two similar female protagonists that question said world, making them both very psychological anime that will make you want to re-watch them to fully understand and put the pieces together.
If you liked
Code Geass: Hangyaku no Lelouch
|
...then you might like
Guilty Crown
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Both series start off with the protagonist (a high schooler) unexpectedly gaining supernatural powers from a mysterious girl who then becomes a strong supporting character for the protagonist. Both also involve mechas, although they aren't the main focus of the show. There are also a lot of crazy plot twists and fatalities thrown through both to keep you on your toes.