Is really good. Humanity fighting for survival in anything other than a zombie apocalypse is a breath of fresh air, and this show is definitely worth giving a try. You can watch the whole series right now for free on Crunchyroll.
The long:
Attack on Titan, or as I like to call it, Attack on Your Freaking Hopes and Dreams
"But Aaron, real fans call it Shingeki no Kyojin!"
Yeah I know, I know. But here's the thing. You try telling your friend to go watch Shingeki no Kyojin and they're going to ask you not to sneeze on them again.
Get it? Because when you say Shingeki no Kyojin out loud it kinda sounds like a sneeze.
The best jokes have to be explained, as well as the best anime.
A little while back I posted my biased review on Sword Art Online, and I still stick by it, it's a great show. *cough* Here's the link to that review *cough* In that review I successfully made someone start watching SAO... and then he didn't stop. I'm doing gods work here people, whether you want me to or not.
So what the hell is Attack on Titan?
Hundreds of years ago the Titans appeared. These giant humanoids that have no genitalia and the most disturbing of expressions on their face showed up and started to eat people. Humanity was no match for the Titans as the Titans had size, numbers and the ability to heal any wound. So basically they were OP as shit.
In a last desperate attempt humanity built three giant walls taller than any Titan and lived inside those walls in peace. But everything changed when the fire nation attacked.
Okay, no fire nation, but there was a colossal titan that appeared and kicked a giant hole right in the first wall, allowing Titans to come into the town of our protagonist, Eren Jaeger. The poor kid had to watch as the Titans destroyed his hometown and barely made it out alive. Eren swears that he will kill all of the Titans after he and his friends are evacuated deeper into the walls and joins the army a few years later.
That's really the start of the show right there, heck you don't even have to watch the first episode (you should though, and you can find it here.)
Like most anime this show is an adaptation of a manga series that's still going on. The anime makes it about halfway to where the manga is at in the story and stops there.
The show is a very good watch, but don't expect it to go easy on you. If you know anything about Game of Thrones and its tendency to kill off people you like then go into watching Attack on Titan with that mindset. It is truly a story of survival and hopefully you can survive the several smacks in the face it gives you.
That's pretty much it, like SAO you can find Attack on Titan streaming for free (with ads) on Crunchyroll. You can also read the manga for free on Crunchyroll if you've decided that the anime didn't give you enough.
I leave you with the shows stellar opening that's been stuck in my head for the greater part of two weeks.