Metal Gear Solid 3 themehttp://www.youtube.com/watch?v=rNVCD1dsnJI
Half Life 2 (beta)http://www.youtube.com/watch?v=qyKcicpkRfU
Iwould have to say the Helo theme. Just love it....
Anything in Jet Set Radio and Jet Set Radio Future.
Metroid Prime: Zero Mission soundtrack. Mainly the Phendrana Drifts theme.