Man... o.o
That's a really hard question >.<!!! though it's curious because i was thinking about that like a hour ago...
I'd probably have to go with these...
Spoiler:
Ayu's got a lot of rock songs, but my favorite is for sure Rule. i love everything about it; the music (so hard!!! yessss :mischievous) the lyrics, the video... everything is just great in so many levels
In the other hand, i really love moments. That's a song that is very close to my heart. Same goes for criminal, that song is really special to me 'cause it reminds me a very special moment of my life