The Main Theme isn't bad either. It's also fairly original for a sci-fi game.
This Theme from the game, used only at a handful of points in the game.
Ground Control 2
The opening cutscenes of several missions. To list a few:
"Rat Catcher": We're introduced to a very well done cutscene of both NSA and Imperial forces firing off at each other in the city, with explosions going off around both of them.
And in that same mission, once you secure the pod's crash site and Centurion Dracus arrives with more of his troops, Major Grant sends you 5 Recon Terradynes to aid you, while the Main Theme plays.
"Calling the Shots": After the initial scroll across the beach of Gideon's Landing, we get the sight of several APCs moving across the watery terrain while explosions go off around them, and awesome music playing in the background.
"Stealing Beauty": You're treated to several large columns of Terran forces advancing through the icy plains on their way to the Research Facility you need to defend.
"She Sells Sanctuary": After the somewhat boring scroll across the prison island, you see Barracuda Flight (five Transport Helidynes) flying towards the back area of the island, towing your troops, all while their pilots chit-chat.
Destroying the TX-3 Anti-Orbital Cannon in "Aiming for the Teeth"