The trailer for Deus Ex: Human Revolution features "Icarus" by the game's composer, Michael McCann. Even better, the DX:HR website now has it available for free download due to the interest in it. The full version of Icarus plays over the end credits. And it is glorious.
The ambient theme playing while in the Sarif Industries HQ (also doubles as one of the menu themes) is very soothing and peaceful.
Pretty much the entire soundtrack qualifies, as well. Enjoy.
The music when you enter the Tai Yong Medical office in Upper Hengsha. It starts off as breathtakingly beautiful and relaxing before suddenly crashing into an intense and epic track, perfectly capturing the intense fights you could get into against the Belltower guards.
The Mole, which feels like it's channelling Deus Ex with some of the better parts of the Mass Effect trilogy soundtrack.
It's fan music, but Miracle of Sound's 'The New Black Gold qualifies. The tune of the song fits in perfectly with the game's actual songs and the lyrics ring true to the game's struggles. Now has an improved version in celebration of his 100th video.