One Piece has great music whether it's from soundtrack or from its OP&ED
Here are a few of my favorites
Binks' Sake (sung by the strawhats)
http://www.youtube.com/watch?v=TM8cvlhFOog
4th Ending Shouchi no Suke (my favorite ED
)
http://www.youtube.com/watch?v=meowqZqakK0
One Piece Opening 11 Share The World
http://www.youtube.com/watch?v=MUWVMR9xLLs
Sogeking
http://www.youtube.com/watch?v=yxUyuj3bUJ4