Blue Exorcist - Son of Satan decides to become an exorcist. Wacky hijinks ensue. My favorite so far.
Gosick - He's a Japanese exchange student. She's a Goth Loli. They solve mysteries in post-Great War Europe. Recommended.
Gintama - Instead of the Meiji restoration, aliens invaded. Hilarity ensues. Opening sequence definitely recommended.
Space Pirate Captain Harlock - Title says it all really. A classic.
Galaxy Express 999 - No one in this world ever gets what they want, and that is beautiful. Everybody dies frustrated and sad, and that is beautiful. But watch some Harlock first.
Sengoku Otome (a.k.a. Battle Girls) - Perfectly ordinary Japanese school girl is transported back into time to warring states era Japan. Where, for some reason, everybody is female (except the talking dog). Total guilty pleasure.
11 Eyes - Interesting premise that doesn't quite pan out. Bonus points for the Hungarian.
Tono to Issho - Japanese history as it didn't actually happen.
Panty and Stocking (with Garterbelt) - Gainax.
Astarotte's Toy - Ten year old succubus needs a harem.
Hanasaku Iroha - Girls at an inn. Maybe something happened? I don't remember.
Bridge to the Starry Skies - I got bored half way through and stopped watching.
We Without Wings - Did you know black people always speak in rap? Also, rape, ha ha ha!
SKET Dance - The one episode I watched was the sort of farce I hate, but it seemed like the series might have potential.
My Everyday Life - Fake Azumanga.
Let's Play! - Alien cat girls invade Earth for Korean BBQ. Why can't I stop watching?!