Well for me it is whatever their current song happens to be.
But then again it would depend on which full length album, mini album or single we are talking about. I often say I haven't heard a Beast song that I don't like.
However, my ultimate favorite Beast song is the one that got me hooked on K-Pop in the first place. I could listen to it 100 times in a row and never get tired of it.
Well I hope you enjoyed Day 2 of the Beast 30 day challenge - I know I did. Please tune in for day 3.