This is a lot, but let me try xD ... in no particular order:
untitled ~for her~
GUILTY
(don't) Leave me alone
Mirror
talkin' 2 myself
alterna
decision
Together When...
MY ALL
kiss o' kill
1LOVE
JEWEL
Born to Be...
Ladies Night
is this LOVE?
STEP you
Because of You
HEAVEN
Will
fairyland
my name's WOMEN
evolution
Moments
HANABI
HANABI ~episode II~
forgiveness
No way to say
Memorial address -take2 version-
Free & Easy
Real me
Voyage
NEVER EVER
Endless sorrow
Duty
M
POWDER SNOW
A Song for XX
(miss) understood
RAINBOW
(Bear in mind I've only heard Memorial address, (miss)understood, Secret and GUILTY in full). I really can't group which are at the top, top.. but this are my all time faves
And of course, the list goes on!