Carry several Ziplock FREEZER bags (they're tougher than storage bags). There's an infinite number of ways to use them. The OP suggested using a Mtn House bag as a bed warmer. I suggest putting it inside a Ziplock for extra safety. A wet bed doesn't sleep well.
Extra flashlight? Ever tried changing a bulb in the dark? At least LED's rarely need changing but even batteries can be a trick when you're blind.
Add in a couple Cyalume sticks to the inventory. One over your kill site works wonders on finding it in less than ideal light. They also work great to help change batteries/bulbs, and on the back of your pack (or your buddies) provides an easy visual reference as to location in the dark. They weigh almost nothing, take up very little space, and when needed, they are more than worth it.
