I'm a huge fan of Hedgehog Heaven, remixes of Sonic the Hedgehog 2 titles.
My favorite has to be Oil Spill by Analoq, a remix of Oil Ocean Zone.
http://youtube.com/watch?v=Kc7eCq51K0g
Beautiful. Just beautiful.
Also, I have to mention Metroid Metal. I really have no words, but the least I can do is give a link to the site.
http://metroidmetal.com/songs.html
Enjoy!