Here are some Halo 3 transcriptions to the halo 3 variation on the trailer:
Similar to mine exept for the fact that I hold the "E" notes, and his timing is just a bit off. This is the Halo 3 piano solo transcribed by The Garbage Man and many other songs on halo as well. Note he only has sheet music for siege of madrigal and the fanfare. The rest are recordings that you can hear on a quicktime player.
Another transcription done by Jayshum of the Halo 3 trailer he has provided us with a recording, the sheet music, and a piano diagram which shows you what keys to play if you do not know how to read music. Note: the sheet music is called "piano dots".
UPDATE: You can now view my version in PDF and Finale Notepad 2003.