Iconic.
This song is over 4 years old. 4 fucking years. How this doesn't have a 5 I don't know. I first heard this as the "Last Human" song from NoXiousNet Zombie Survival on Garry's Mod years ago. They've since changed the Last Human song several times, but I found out recently this was still on my HD. I slapped this in the right folder and a big shit-eating grin came across my face when the humans were whittled down to one and this started playing.
I can't stress enough the atmosphere you've captured with this piece; dread, terror, you're fucked, etc. This fits so seamlessly into a Zombie environment- the moans and wails of the undead compliment the song like they were mixed there in the first place. Of course due to the nature of the game, the last human is at a distinct disadvantage against a crowd of undead, so most games they don't last for more than 30 seconds, which is disappointing. Every time one survivor remains I always hope that they put up enough of a fight for me to truly enjoy this badass motherfucker of a song.