I may have changed this from my original idea. Maybe. Because I'm fickle. You'll all get Cloud Age Symphony another time...
I've heard multiple different versions of this with different additional instruments, and of all of them I consider this to be the best due to the inclusion of the additional melodic line from the piano. It adds a counterpoint and depth that reinforces the other elements rather than competing with them, raising the overall song to new heights. In my opinion : )
Artist: FictionJunction featuring Yuuka | Composer: Yuki Kaijura | Show: Gundam SEED Song: Akatsuki no Kuruma
I particularly like this song not least due to the alterations in melodic pacing through the duration and the more instrumental provision of the music, but also a particular scene from the anime that it supports: the launch into space of the main characters to begin the final arc of the series. Spoiler Warning.
With the slower section occurring as the final preparations are completed and the Archangel ([cough]WhiteBase[cough]) departs, the pacing picks up as the attack upon the launch catapult becomes imminent and the decisive minutes approach. The song really provides that sense of desperation and rapidity the scene goes for; Cagalli (the blonde) being thrown onto the escaping ship and being distracted with a revelation about the core cast long enough for her saety to be ensured over her stubbornness, the two Gundams fighting to delay the encroaching enemy just long enough, knowing they have to make it to the ship as it races down the track or else be left behind, the ship itself betting on speed and shock to manage to launch before it can be destroyed and take any hope of overall victory with it... Feeling of loss, desperation and determination pour from the music and work the scene into one that marks a personal highpoint of anime in general for me.