Code Geass isn't the "sci-fiest sci-fi" and with some of its aspects it might not be the best pick for some, but I'm sure it has a lot of fans as it was given many awards in 2007 and 2008. It is mecha anime, the main fighting power are the Knightmares.
The story is about a rebels fighting the occupation force Britannia empire. The rebels joind their forces with strategicly thinking Zero, whos thinking is very similar to one of chess player. He has a superpower, he has a vision and he also has a history, which noone knows. Often the story takes us to the imperial university full of spoiled girls thinking about their problems not seeing one country, one nation being oppressed by the empire.