Attack on Titan
It's rare that an anime actually gets me angry because it's only two episodes into the series, but that's how incredible Attack on Titan is. This show is amazingly awesome, I can barely believe it.
Okay, so the setting is a semi-medieval period (I say semi-medieval because, while no real machine per se exist, they still have some interesting gadgets I'll get into later) and in this world, people live inside a walled off city. Why is it walled off? BECAUSE GIANTS ROAM THE OUTSIDE WORLD AND EAT HUMANS FOR SEEMINGLY NO REASON. While the giants have no reason to eat people, as they don't really seem to NEED to eat, they do it anyway, as if it's an instinct to them. A young boy named Eren sees his life turned upside down the day a fifty meter-tall titan attacks and actually breaches the wall that had protected the city for a hundred years. The poor boy even sees his mother gruesomely eaten by a titan before his eyes. As he witnesses the destruction the titans are capable of first hand, he vows to kill every last one of them, joining the army to do so. He's accompanied by Mikasa, his adoptive sister, and Armin, his best friend, both of whom have pretty much the same reasons as he does for hating the titans.
What's very cool about this show is that the titans are so mysterious: None of them have genitalia and yet their numbers keep rising; None of them talks and, in fact, none of them seem to be very intelligent, so what's their reason for being and for eating tons (And I mean TONS) of humans when they don't even need to to survive? Is someone creating them? I like all the characters so far: Eren, while being sort of the usual gutsy kid that bark a lot but doesn't even have the strength to fight (yet) is very likeable and the anime makes it easy for us to sympathize with his quest for revenge. Mikasa is by far my favourite: She has kind of a Rukia Kuchiki feel to her where she's very serious and collected and wants to protect the ones she cares for (i.e Eren) though it's obvious there's more to her, not only because adopted kids in anime ALWAYS implies a dark or troubled past but also because she mentions, while escaping the rampage of the titans on boat, that 'this seems familiar'. Armin, while acting sometimes cowardly, does so only to avoid pointless conflict, showing a level of intelligence not displayed by say Eren and as such makes a good match for the hot-heated protagonist. There's also an odd mystery surrounding Eren's father who seems to have performed some odd experiments on his own son, though they have yet to elaborate on that.
I urge you all to check out this excellent show, though fair warning: Not for the faint of heart.