Hope this is allowed... If I don't make it, it's going to be made a million times, so it might be a nice topic to sticky. =P

My favorite anime/manga is One Piece.

My other favorites (in order) are:
Trigun
Fullmetal Alchemist
Ouran High School Host Club
Monster

Explanations are nice. I'll probably edit this later to add mine.

Definately Higurashi and Lucky Star.

Lucky Star is annoying for me...no offence.

One Piece owns

My favorite Anime is Code Geass.

Soul Eater

How the hell could I possibly have a favorite Anime with as many as there are out there ._.?

Ctrl+C and then...

Bleach, Code Geass, Cowboy Bebop, Crest of The Stars, Elemental Gelade, Escaflowne, Fate/Stay Night, Flame of Recca, Fullmetal Alchemist, Hunter X Hunter, Inukami!, Inuyasha, Kenichi, Kiba, Mai Hime, Mar, Murder Princess, Naruto Shippuuden, Ninja Scroll, Onegai Teacher, Outlaw Star, Saber Marionette J, Scrapped Princess, Shakugan No Shana, Shonen Onmyouji, Tayutama Kiss on my Deity, This Ugly Yet Beautiful World, Tsubasa Chronicles, Vampire Knight, YuYu Hakusho.

This thing keeps going and going and going and going......

Manga:
- Fullmetal Alchemist
- Gantz
- Soul Eater

Anime:
- Fullmetal Alchemist: Brotherhood
- Soul Eater
- Cowboy Bebop
- Fullmetal Alchemist

Both lists ordered most to least.

Manga : Angel Densetsu ( EPIC LOLZ)

Anime : Excel Saga ( extremely retarded)

these are both series I actually start laughing out LOUD at my computer while watching /reading them

Lucky Star, Elfen Lied, and Code Geass.