Probably a decent idea to list what you've seen so we don't mention it, but here's my list of a few things I've seen and enjoyed:

Bleach
Death Note
Fullmetal Alchemist: Brotherhood
Soul Eater
Tokyo Ghoul
Assassination Classroom
Kill La Kill
Cowboy Bebop
Code Geass 
Attack on Titan
The Future Diary

Thats probably a third of what I've seen. Just seen Blue Exorcist a couple days ago and thought it was decent but nothing as good as other stuff I've seen.

Fav out of the bunch would have to be FMA:Bro. That story just held me so much until the end, and when you think, "No, they're not gonna do that" with story climaxes, they do.