The first song is the overall theme for the Apocalypse...
1. Down With The Sickness - Disturbed

The second song is what plays when you kill your first zombie...
2. Y'all Want a Single - Korn (It has the anger I would need)

The third song plays when getting chased by a horde...
3. One Trick Pony - Deadmau5 (Tecnho = fastbeat = runnng fast)

The fourth song plays when you have to kill your loved one...
4. Forget Me - Violet Columbus

The fifth song plays when you find a group of survivors...
5. Too Much Too Young Too Fast - Airbourne

The sixth song plays when you meet a new love interest...
6. Use Me - Bill Withers (Oh yeah...)

The seventh song plays when you have to make a final stand...
7. Raise Your Weapons - Deadmau5

The eighth song plays when you think you've survived it all...
8. Harder Better Faster Stronger - Daft Punk (Is it not a win song?)

The ninth song plays when you discover a bite mark on you...
9. 10 Years Today - Bullet for my Valentine (It's about suicide...)

The tenth song plays over the end credits...
10. Into the West - Annie Lennox