In no particular order:

1. BURN
2. one piece
3. Hitotsu Dake
4. Haruka
5. BEAUTeen!!

1. SCANDAL BABY (masterpiece)
2. Doll
3. Harukaze
4. Shoujo s
5. Space ranger

5. Sakura Goodbye
4. BEAUTeen!
3. Harukaze
2. Shunkan Sentimental
1. Taiyou to Kimi ga Egaku STORY

my list :

1. harukaze
2. pride
3. shunkan sentimetal
4. hi hi hi
5. shoujo s 

^^

1. Right here (I don't think this song is very famous from them, but I like it a lot, they sang in English a bit too.)
2. Awanai Tsumori no, Genki de ne. (Love this song)
3. Satisfaction
4. Burn
5. Most of their songs.

1. Awanai Tsumori 
 2. One Piece
 3. Koe
 4. sono toki sekai wa kimi dake no rain
 5. SCANDAL BABY

I really like it when mami sings!

another Update!

now is: 1 - Harukaze
2 - One Piece
3 - Welcome Home
4 - Taiyou To Kimi Ga Egaku Story
5 - Shunkan Sentimental

1. awanai tsumori no genki de ne
2. right here
3. love survive
4. queens are trumps
5. rock n' roll

1. Queens are trumps
2. Awanai Tsumori no, Genki de ne
3. Shunkan Sentimental
4. Rock n' Roll
5. Shoujo S

... All their Rock songs, All their Soft/mellow songs, and All of their cover Song.

1. Welcome home - the lyrics are very meaningful and somehow nostalgic 
2. Awanai tsumori no, genki de ne - meaningful lyrics and just an awesome rock song 
3. Sparkling - this song always lifts up my mood, watch the ontama live theres lots of energy
4. Satisfaction - its such a catchy song, woah oh woah oh
5. Aitai - just an awesome song

Most of my favorite songs are classics, hehehe .sweat.

1. Space Ranger
2. S.L. Magic
3. Koi Moyou
4. Anata Ga Mawaru
5. Playboy

1.SHUNKAN SENTIMENTAL
2.HARUKAZE
3.ONE PIECE
4.BITTER CHOCOLATE
5.BEAUTEEN

hardest part to choose what is their best song for me. xD

Countdown .clap.

5. CUTE!
4. Queens are Trumps
3. Nanka Buttobase
2. Doll
1. Shunkan Sentimental

gave equal attention to each album

In no particular order (because this is very hard for me):

DOLL - This puts me in the mood so fast. Haha.
Taiyou to Kimi ga Egaku Story - Something about this song that always makes me happy when I hear it.
Happy Collector - My favorite B-side!
Bright - I always feel like I've heard the melody before, or maybe I just love it so much.
LOVE SURVIVE - Well, uhmm, obviously.

Those are my favorites (but it was hard to choose ^^"):

1. Space Ranger: Love the energy and enthousiasm that the song convey (I am like that most of the time ) and what's more, I am fond of the PV song and I like pretty much their schools uniforms style!^_^
2. Beauteen: also a good energic song that makes me wanna smile and dance!
3. S.L Magic: a simple garage rock song but so flamin' good.
4. Shoujo M: love the electro vibes of that track and Mami's voice!
5. Awanai Tsumori no Genki de ne: a good effective rock song.

Ok let's see,
1. Awanai Tsumori no, Genki de ne
2. Kagen no Tsuki
3. Harukaze
4. Love Survive
5. Koe

I love how everyone's favourites are different! It just goes to show they have a lot of good songs and can branch out to appeal to a lot of people and different tastes! There are too many that I like but notable classics are SCANDAL BABY (perfect), Shoujo S, Kagerou, Koe, Kimi ni Shitto Chuu, Anata Ga Mawaru, Emotion and Rising Star

1. HARUKAZE
2. SHUNKAN SENTINMENTAL
3. LOVE SURVIVE
4. PRIDE
5. TAIYOU SCANDALOUS

can't sort it by order, i love all their songs, but here is 5 most mine
- Taiyou To Kimi Ga Egaku STORY
- Kagerou
- Aitai
- Bright
- Scandal Baby

My TOP 5!!!!
1. Harukaze - I'm in love with lyrics and melody of this song  
2. Scandal Baby - this was my 3rd song of SCANDAL
3. Queens Are Trumps - Intro/Riff is amazing <3 and the lyrics are by MAMI!! 
4. Haruka - Very emotional song.. i like to listen to it in a rainy day :3
5. Taiyou SCANDALOUS - I love this song's guitar solo part  and i'm always in a good mood while listening to ^

Updated my rankings and here are my top 5 so far...

5. Awanai Tsumori no Genki de ne
4. Bitter Chocolate
3. Sayonara My Friend
2. Weather Report
1. BURN

because Weather Report has that greatly-written lyrics that it went in my 2nd spot haha

Update with the new album coming out (or rather, arrived at my doorstep )
5. HARUKAZE
4. Uchiagehanabi
3.Haruka
2. Awanai Tsumori no, Genki de ne
1. Kagen no Tsuki

Uchiagehanabi might climb more, with more listening (this song clicks right in ever since I've played it XD)

My Top 5

5. Queens are Trumps
4. Metronome
3. Burn
2. Koi Moyou
1. STANDARD

But there are much too excellent songs.

Here is mine :3

5. BEAUTeen!!
4. Playboy Part II
3. Everybody Say Yeah!
2. Scandal Baby
1. STANDARD

but actually I'm crazy about BEAUTeen!!