Too many to think about for long, so off the top of my head:
Blood pumping, frenetic, calming, remorse, it has it all.
Exploring the rooftops with music in the background is a large reason why this is one of my favorite games. Just enhances the game so well, and is easy to listen to outside the game.
2 selections of the best WOW has to offer. One eerie and perfectly highlights a nation's fall from grace, the other a sense of adventure in a hostile land.