Invisibly Shaken is my new favourite country song. It's by Rodney Atkins and it speaks of a man who is calm and collected and cool on the outside but on the inside he is shaken and torn because his woman has left him. I think his voice trembles and sings with a raw pain that is almost tangible (of course, it may just be the timbre of his voice but having never heard any of his songs before, it is believable to me that his emotions are pouring out)
The song rhymes (which is a big plus for me, hahahahah) and I think the lyrics sound realistic - what someone WOULD go through in a break up.
Here you can find a review of the song and his albums.