Never Surrender
From Halopedia, the Halo wiki
Never Surrender is a song by Nataraj and Nile Rodgers included in the Halo 2 Original Soundtrack. The song contains techno-remixes of the Halo theme, including the theme's opening monk chant.
In addition, sections of Steve Vai's MJOLNIR Mix are heard. This song is not heard during the Halo 2 gameplay. It includes Cortana extracts throughout the song, and ends with her saying "That's it, I'm shutting you down!" It is unknown what she is shutting down, but this could be a reference to the music begin "shut-down".
It is also included as an Easter Egg in the Halo: Reach level, New Alexandria.