Aside from the mainstream ones such as Naruto, One Piece or Fullmetal Alchemist, I really enjoy Hellsing, Basilisk, Rurouni Kenshin and (for something more fun to watch) Kochikame.
If you don't mind anime movies, you
must see 5 Centimeters Per Second and any of Hayao Miyazaki masterpieces. Howl's Moving Castle is a favorite of mine.
againstall has invadedBECKY = 10/10