Crap, that's what instantly came to mind when I first read the thread title. That's exactly what should be playing whenever I am running around an arkfall.
As a 2nd choice, I'll have to go with the old stand-by:
http://www.youtube.com/watch?v=AFa1-kciCb4
Semi-related side note: Every time I hear one of the rapid-firing infectors, it reminds me of the beginning of this:
http://www.youtube.com/watch?v=iiTCTsTyjdw

