ending: hare hare yukai (haruhi suzumiya) definitively
opening: motteke serafuku (lucky star)
19sai (xxxholic)

For the best opening or ending song, period..it's a difficult choice but I'm gonna go with Anna ni Issho Datta no ni from Gundam SEED. This song can literally make me cry.

D-tecnolife(Uverworld)/Bleach , HoukiBoshi(Younha)/Bleach , Shounen Heart(Home Made Kazoku)/Eureka 7 , Season's Call(Hyde)/Blood + , Aozora no Namida(?)/Blood + , Shinjitsu no Uta(Song of Truth){?}/Inuyasha , Fukai Mori(?)/Inuyasha , Tsumasaki(Ore Ska Band)/Bleach

Openings:

Cruel Angel's Thesis (Neon Genesis Evangelion opening)
THE BEST!

PRIDE (Gundam Seed Destiny opening)
Destiny sucks for sheer emotion, but this rocks!

Melissa (Fullmetal Alchemist opening)
I HATE ELRIC; I LOVE PORNO GRAFFITI!

Endings:

None. The Japanese give excessive attention to openings, and let the endings rot.

Ergo Proxy, Blood+, Tsubasa Chronicle, Fullmetal Alchemist, Mobile Suit Gundam SEED/DESTINY, D.N. Angel, Black Cat, Fafner of Azure, Eureka Seven

Motteke sailor Fuku
Opening of Lucky Star

*0*

Openings
Code Geass - Colors
Bleach - D-tecnolife, Asterisk, D-tecnolife, Rolling star
Gundam Seed (&Destiny) - Moment
Tsubasa Chronicle - Blaze
Loveless - Tsuki no Curse
Inuyasha - Change the World & One Day, One Dream

Endings
Loveless - Michiyuki
Code Geass - Mosaic Kakera
Gundam Seed (&Destiny) - Reason, Find The Way & Life Goes On
NANA - Winter Sleep & A Little Pain
Full Moon - Eternal Snow
Inuyasha - My Will, Fukai Mori & Every Heart

+ Naruto, FMA etc etc.

X3.

Opening:
Mai Otome - Crystal Energy
Air - Tori no Uta
Shakugan no Shana - Being
D.C.S.S. - Sakurairo no Kisetsu
Card Captor Sakura - I am a dreamer
Sola - Colorless Wind

Ending of Juuousei : Te wo Tsunaide by younha

Quote by xXZeroMeowXxthe best opening that i have heard was probably
Ergo Proxy- kiri

ur right ,I think that kiri is the best OST ever (thought I have a limited ANIME experience ,cauz I read more manga than i watch animes)
Also berserk OSTs where good 2 especialy "Forces"

D-Tecnolife (Bleach)
Colors of the Heart (BLOOD+)
Ready Steady Go (FMA)
Go (Naruto)

Fma- The last opening song.
Fma- the first ending song. (I suck at the names)

0:00 am
~Tokyo Majin Kenpuchou tou

dunno,, i love that anime..

The opening to Trigun is still very memorable; I guess the first series you watch sticks with you, but I've seen a lot of anime, and it's still pretty awesome after all this time.

Any songs by ALI PROJECT or Yousei Teikoku are pretty amazing. Also cute hyper songs like the end song to Magical Pokan are cool ;D

For opening hmmm Tank! - Cowboy Bebop, Rose - Nana, Chain - Air Gear...Those are just amazing!

As for endings...Be your girl - Elfen Lied, My World Down - BECK (all BECK music was good haha) and Gravity - Wolfs Rain

Here are some of my favorites. Not in any particular order except the first ones, which are the best themes I have heard so far.

Opening themes:
1. Tie between Rewrite (Asian Kung-Fu Generation) and GUNxSWORD (composed by Nakagawa Koutarou featuring Ondekoza), Fullmetal Alchemist and GUNxSWORD
2. Sakura Kiss (Chieko Kawabe) - Ouran Koukou Host Club
3. Blaze (Kotani Kinya) - Tsubasa RESERVoir CHRoNiCLE
4. Disillusion (Tainaka Sachi) - Fate/Stay Night
5. Colors of the Heart (UVERworld) - Blood+
6. Hajimari no Kaze (Ayaka Hirahira) - Saiunkoku Monogatari
7. Ready Steady Go (L'arc~en~ciel) - FMA
8. Aozora no Namida (Hitomi Takahashi) - Blood+
9. Pika Pika no Taiyo (Kana Ueda) - Gakuen Alice
10. Sakasama no Chou (SNoW) - Jigoku Shoujo

ED:
1. Shissou (Last Alliance) - Ouran
2. Kazemachi Jet (Sakamoto Maaya) - Tsubasa
3. Anata ga Ita Mori (Jyukai) - Fate/Stay Night
4. Calling You (Okino, Shuntaro) - GUNxSWORD
5. Kesenai Tsumi (Nana Kitade) - FMA
6. Tobira no Mukou E (Yellow Generation) - FMA
7. Come (Namie Amuro) - Inuyasha
8. A Rising Tide (Okino, Shuntaro) - GUNxSWORD

...yeah.

OP: Yoriko - Daia no Hana (Black Cat)
ED: Kawada Mami - triangle (Shakugan II)

the OP I can completely back, but I haven't really listened to many EDs so...

OP - SCRAMBLE (1st season of School Rumble)
Lilium (Elfen Lied)
Minami-ke's OP (don't know name...)
Aozora Loop (Kimikiss Pure Rouge)
ICHIGO Complete (Ichigo Mashimaro) was a good choice for that type of anime, though it's not my type of music

The only ED I remember liking is Kesenai Tsumi from FMA just because I bought the OST. Dango Daikazoku from Clannad was also nice to watch.

air opening and tsubasa chronicle first season ending

My favourite opening is Hikari (Inukami)
My favourite ending is the ending of DearS.

"Sexy Sexy" by Cascade, Ending theme for Ghost Stories. Best. Ending. Ever.

Hm there are many OP+endings I like.. But I think the best is the OP from GitS.. the song was sung from Origa, and it's called "Inner Universe" .. the voice and lyric is awsome

There's too many darn good songs but for OPs I like Blaze by Kinya..loved that soaring feel and pick-ups.For endings I like Half-pain from Witch Hunter Robin.Soothing and had really deep meaning to me.