Might as well start with the Queen of K-pop!
The above track is "Not Over U" by BoA. It's off of her wonderful "Only One" album, one of my favorite k-pop albums of all time. And I'm not doubting that Hurricane Venus/Copy & Paste were good albums because they were, but BoA kept things short, sweet, and casual with "Only One." With that said "Not Over U" is my favorite track (outside of the two title tracks) on "Only One." I love the mixture of the warm acoustic guitar notes against the pop/techno sound. It makes for a very great hybrid of a song worthy of many listens and gets me in the mood for dancing.