Epic... Powerful... Absolutely MOVING Songs!

Megalith -Agnus Dei- - This is one of my all time favorites when it comes to epic music. I was glad it had such a high ranking in the GFF Best song of 2005. I havent even played AC4 and yet I really enjoy this song. The whole opening just screams OH SHI~ Boss Fight to you, right from the start it makes you feel like you are standing against the main badguy or a really huge monster that threatens to devour you in an instant. And then the fight rolls on, with the slowdown after 3 minutes to enter a new mode of the fight and then just slowly gear up into high mode again. An excellent song that just eminates epic.

The Unsung War - I absolutley love this song. I hadnt even played AC5 before I heard this one, but still as in the case of Megalith I managed to fall in love with this one. This is great because of the buildup in a slow momentum. One can almost imagine the planes lining up on the runway and taking off toward the epic battle that will sway the tide of the war.
Now I just wished I had played through AC5 when I had the chance.

And I might as well add Reprisal from AC5 to the list. I didnt like it in the beginning actually. But now its grown on me and I find it really really good.
Other great ones that has to be mentioned is Blockade from AC4, First Flight (it really doesnt sound like a remade version of Blockade) from AC5. And the most obvious one, Hell March from C&C Red Alert. Might as well toss in Hell March 2 from RA2 as well.

Jam it back in, in the dark.