The song I'm currently caught up in listening to is the song "Siege" from the Call of Duty: Modern Warfare 2 soundtrack that I purchased yesterday.
It's quite an interesting piece, and it goes with how the game goes of starting slow as you see wounded soldiers, and it climaxes when you get out of the trenches to see Washington, D.C. in flames and under attack.
It certainly is a beautiful and emotional piece that I would recommend, especially since the soundtrack is composed by Hans Zimmer and Lorne Balfe. When the volume is cranked up on the stereo or headphones, the emotional power of the work is revealed, resulting in quite a few goosebumps to me.
This is pretty much the anthem of Sonic the Hedgehog's anniversary last year. Read the lyrics while the song plays to notice the heavy influence of the last 20+ years of Sonic history!