actually I like them all, can't really decide which one is the best (or my hearing is getting worst?)

secret of my heart => 9th ending song
i can't stop my love for you => 10th opening song

I agree with Secret & I can't stop my love...

My favorite opening is the 16th : Growing of my heart
My favorite endings are : the 9th Secret of my heart and the 12th, Always!

i like Magic by Auichi Rina

I rly like a lot of them...just to name a few there would be opening 27 - Magic, opening 5 - Truth and opening 7 - Mysterious eyes.
The movie theme songs are also rly good, especially movie 8's ending theme Dream x Dream by Aiuchi Rina. I quite like her songs and she has sung quite a few DC theme songs including I can't stop my love for you, also a rly good one! XD

I have so many favorites :D

Opening:
Magic - Aiuchi Rina

Ending:
Secret of my Heart - Mai Kuraki [My very first fav. DC song]
Yume Mita Ato De - Garnet Crow
Summer Memories - Kamiki Aya
I Still Believe - Shizukusa Yumi
Tomorrow is the Last Time - Mai Kuraki
Hikari - Breakerz
Hello Mr. Yesterday - Hundred Perfect Free
Juugoya Kuraishisu~ Kimi Ni Aitai~ - Hundred Perfect Free

Also its cool theme song: Kimi Ga Ireba
and the 'insert' song. lol - Ai Wa Itsumo

:D

waga routashi aku hana - ending theme code geass r2
still for your love - ending theme detective conan
a song of chivalrous youth - ending theme code geass r1
northern lights - opening theme shaman king

Revive by Kuraki Mai
Magic by Rina Aiuchi
Tomorrow is the Last Time by Kuraki Mai
Hello Mr. My Yesterday by Hundred Percent Free
Always by Kuraki Mai
Summer Memories by Kamiki Aya

magic - aiuchi rina
secret of my heart - mai kuraki

And so many more............

私は生活の中で倉木麻衣のスタートのように私だと思う。

Unfortunately, I can't just choose one. There are many good ones:

Openings:
Unmei no Roulette Mawashite
Truth ~A Great Detective of Love~
Mysterious Eyes
Kimi to Yakusoku Shita Yasashii Ano Basho Made
START
Hoshi no Kagayaki yo
Growing of My Heart
Everlasting Luv
MAGIC

Endings:
Koori no Ue ni Tatsu You ni
Secret of My Heart
Overture
Kimi to Iu Hikari
Wasurezaki
~June Bride~ Anata Shika Mienai
Sekai Tomete
Sekai wa Mawaru to Iu Keredo
Doing All Right
Tomorrow Is The Last Time
15ya Crisis ~Kimi ni Aitai~

1st opening:mune ga doki doki

kanze no la la la
opening grawing of my heart
aya kamiki(Zard)black and red cruch
destiny
winter bells

ending secret of my heart
always
thank u for every thing

a mi me gusta truht

i like feel your heart and nazo too!!

Magic-Rina Aiuchi :D
I never get bored to hear that song :)

Truth for me not sure about the closing cause i what not happy when the show ends

1. SECRET OF MY HEART - MAI KURAKI
2. SUMMER TIME GONE- MAI KURAKI
3. REVIVE- MAI KURAKI
4.MISTY MYSTERY
5.FEEL YOUR HEART
6 MYSTERIOUS EYES- GARNET CROW
7. AS THE DEW- GARNET CROW
8. SUMMER MEMORIES
9. HELLO MR.MY YESTERDAY

Misty Mystery :)

Opening
1.Winter Bells
2. I Can't Stop My Love For You
3.Kaze No Lalala
4.Growing Of My Heart
5.Namida No Yesterday
6.Mysterious
7.Everlasting Luv
8.Misty Mystery
9.Summer Time Gone
10.Don't Wanna Lie
11.Kimi No Namida Ni Konna Ni Koi Shiteru
12.Try Again

Ending
1.Still For Your Love
2.Secret Of My Heart
3.Natsu No Maboroshi
4.Always
5.Yume Mita Ato De
6.Mushoku
7.Wasurezaki
8.Summer Memories
9.Hello Mr My Yesterday
10.Tomorrow Is The Last Time
11.Your Best Friend

I LOVE ALL CAN'T CHOOSE XD