Definitely, "Take A Bow". It's so different from other Korean songs because of the music. Mister is the second song that made me go wow, but that was after the performances for it. :x
I'm glad DSP changed their image and gave KARA some room to grow. I'm sad about the type of songs on the album though; there isn't an actual ballad or a strong song (a song that sounds fierce and with strong vocals). I'd give the album a 3.5-4.
"Wanna" took me at least 3 listens to get used to it; like many other fans, I was expecting a strong, upbeat song from the teaser.