The title says it all. Feel free to state your favorite piece of in-game music or music from the soundtracks that wasn’t in-game. Or even post a list if you have multiple favorites. (Like I do.)
My favorites are:
“Installation 04” (Halo: CE: Anniversary)
“Heavy Price Paid” and “High Charity” (Halo 2)
“One Final Effort” and “Tribute” (Halo 3)
“117” and “Never Forget” (Halo 4)
“Ghosts and Glass” (Halo Reach)
“Rain” (Halo 3: ODST)
“Halo Canticles” and “The Trials” (Halo 5: Guardians)
My favorite has got to be the original theme song, gives me goosebumps every time I hear it. In fact, when I started Halo 5 up, I let the whole song play through just to soak up the enjoyment for the new Halo game.
All of the songs merge together for me so I just have one big Halo theme in my head.