The title says it all.
I just completed season 2 today (finally) and I love all the music from both seasons. If I had to choose a favorite though, I'd say it's No Thank You. It rocks my face off! ^_^ Originally, Don't Say Lazy was up there. But then, I heard No Thank You and I quickly changed my mind.
What about those of you who are familiar with K-On!? What's your favorite opening or ending song from K-On!? Why?