For me it was Cowboy Bebop.
My first finished Anime (back in the good ol`MTV days)
The theme and the music just left me breathless, as Spike fell down on the stairs wiht his "bang".
FullMetal Alchemist Brotherhood: Most of my questions were answered, the primary antagonist (and most secondary ones) was defeated :D
DeathNote: the final showdown between Light and Near was pretty good. Too bad L himself couldn't finish the job
To be honest, I didn't really like Clannad at all. I loved all the other heroines, except for Nagisa. She honestly was a super uninteresting character, but I guess she was a perfect fit for the main dude.
Anyways, I'd say it's honestly Evangelion. I'd like to say other things are comparably more satisfying, but Eva's hit me the hardest. Code Geass was definitely cool, though.
I think it's death note and fullmetal alchemist brotherhood. I liked the fist one because it had a real ending, it respected the fist assumption the light would be killed by ryuk, and how it gets there( the whole plod, the sacrifice of mello and the mistakes that drove to that ending(why and how it occur). And i liked full metal because it already had a place in my heart and it tould an amazing history, so much deep and diverse compered to the fist one, but the end was really remarkable, the whole world was affected and what happend changed it completely(it closed the jornery and every character was evolved)
Second season of Kuroshitsuji, I absolutely loved how turning Warning SPOILER Ciel into a demon messed up all Sebasian's plans, and made him a servant for some brat for a whole eternity. SPOILER end
I really enjoyed the ending of Clannad and Code Geass. Everything was wrapped up in a satisfying manner and it was a happy ending overall (I don't like sad endings).
Plastic Memories,all the time i kind of afraid they do asspull 'miracle' shits
instead,they really keep the expectation from the first episode about isla's age