I like LotGH, 12K, and Planetes, all very much. But I also like comedies like Hale nochi Guu, Potemayo, School Rumble, and Midori no Hibi very much as well. Then Aria, YKK, Simoun, Mushishi, and Nodame Cantabile are up there. I love war drama like Turn A Gundam, FMP, Macross, and Nadesico. I enjoy overdramatic romance animu like ef, Clannad, and KGNE. I like Lain, GitS, and Alien 9. I have lived on shows such as FLCL, Lucky Star, Trigun, Tenchi, Love Hina, Geass, Ranma, Haruhi, Marimite, Hidamari Sketch, Bottle Fairies, Urusei Yatsura, and Azumanga Daioh. Doraemon, Detective Conan, Cardcaptor Sakura, and Shin-chan can be great too.
Telling me to pick one is impossible.