My hunting pack is starting to look more and more like my emergency pack all the time.
What I've found is I tend to use redundancy as insurance. I have more than one of almost everything, fire kit, compass, knives, wire saws, water purification, shelter, snare wire.
I have most of what has already been mentioned in mine, though my FA kit needs some upgrading. Some things I have that haven't been mentioned yet:
-needle & thread - broken gear or wounds, weighs next to nothing
-glow sticks
-fishing gear - line could also be used for gear or wound repair
-incidentally plastic sewing machine bobbins are great for stowing small amounts of thread or fishing line
-filet knife
-snare wires
-there is a certain brand of metal cup, I forget which one, but they fit on the bottom of a 32oz Nalgene - I have two of each, the cups are about 12-16 oz
-wire saws
-haven't seen a whistle mentioned yet, maybe I just missed it
-signal mirror
-wetfire - individually wrapped tinder, burns even while floating on water- I have tons of it stashed throughout my pack
-I have a kit within a kit on both packs, the hunting pack's is much smaller - basically one of those watertight plastic containers, could use a widemouth nalgene, but it holds all of the absolute essentials - if I had to leave my pack for some reason, my chances with just that small kit are still pretty decent
Like I said, I tend to have at least two of everything. I guess I hold to the two is one and one is none idea on survival gear.
If you are serious about uour emergency pack, check out Creek Stewart's book
http://www.amazon.com/Build-Perfect-Bug-Out-Bag/dp/1440318743