My favorite opening is a tie between "Koi wa THRILL SHOCK SUSPENSE" and "Shoudou". Maybe "Destiny" a little, too.
Now, endings... I mostly like "Step by Step", but I also like "Kimi ga Inai Natsu", "Negai Goto Hitotsu Dake", "Still For Your Love", and "Secret of My Heart". Yes, all but one has to do with a romance. It's mainly because I like that weird sweet feeling you get when listening to something like that.