Being that I just got back from Tokyo and there was Evangelion everywhere (including an entire Eva-themed pachinko parlor), I'm inclined to say Neon Genesis Evangelion. My heart also holds a fondness for Sailormoon.

I'm more of a manga person. My favorite mangas are Mars and Aieru ze Baby (also a favorite anime, I suppose). Dengeki Daisy is also excellent but it's not done yet.