i have no idea how I missed seeing this thread earlier. I guess I'll throw my personal list out if anyone's interested:
Action/adventure:
FATE/Stay Night
Full Metal Alchemist (Original, Brotherhood, Conqueror of Shamballa)
Densetsu no Yuusha Densetsu (The Legend of Legendary Heroes)
To Aru Kagaku no Railgun
Busou Renkin
Black Lagoon
Black Cat
Karas
Soul Eater
High School of the Dead (already mentioned)
Shakugan no Shana
.hack (sign, roots)
Ragnarok the Animation
Rozen Maiden
The Third: The Girl With the Blue Eye
Gunslinger Girl
Grenadier
Law of Ueki
Death Note (How in the world did I forget this one?)
Gakkō no Kaidan
GetBackers!
Yu Yu Hakusho
Dragon Drive
Music:
Nodame Cantabile (for the classically inclined) (Paris Hen, Finale)
K-On (!, !!)
Macross Frontier (Also a mecha series)
Scifi/Mecha:
Tengen Toppa Gurren Lagann (Already mentioned)
Ghost in the Shell (Innocence, S.A.C, S.A.C 2nd gig, Solid State Society)
Code Geass
Neon Genesis Evangelion (Already mentioned)
Horror/Suspense:
Higurashi No Naku Koro Ni (kai, rei)
Puella Magi Madoka Magica (Already mentioned)
Umineko No Naku Koro Ni
Shiki
Tsukihime
Hellsing (Already mentioned)
Jigoku Shojo (Hell Girl)
Kampfer
Seikimatsu Occult Gakuin
Slice of Life (Where plot goes to die, or be resurrected)
CLANNAD (<--- 3 years and it's still my favorite) (After Story)
Lucky Star
Haruhi Suzumiya (Melancholy of, Disappearance of)
Spice and Wolf (II)
Kino's Journey
Bamboo Blade
Kamisama Kazoku
Cross Game
Chobits
Da Capo
Shuffle!
Ouran Host Club
Toradora!
Clamp:
XXXHolic
Tsubasa Chronicles
Card Captor Sakura
Movies:
Ponyo
Howl's Moving Castle (Already mentioned)
Cencoroll
Princess Mononoke
The girl who leapt through time
Paprika (Part of the inspiration to Inception)
Spirited away
I'm not going to mention shonen jump series because I have a love/hate relationship with them
Alright, I'm out of titles off the top of my head. Most of these can be found at animefreak.tv