If you haven't heard their music, you've been missing out. Unfortunately, I don't understand much of what they're singing about (Czech although close, is not *that* close to my native Russian), but the music and vocals are great!

http://www.youtube.com/watch?v=kZf6N3GF4gM&feature=related
http://www.youtube.com/watch?v=QzOfqbvb3Jg (all the other versions of the song on YouTube were from live concerts, so sorry if you don't like CoD4)