Don't know where you'll be hunting, but always, always be ready for the worst! Try the following:
[ul][*] Very, very loud whistle (for signaling, if you get hurt/immobilized or find someone that is)[*] Space blankets (very small packages, very good for improvised tents and warmth)[*] A rescue strobe light -- $15-20, can be seen at night for miles[*] A windproof lighter AND waterproof matches AND cotton balls, in case you need to make a fire
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You'll always have an easier time improvising if you have confidence that you've packed a few survival items along. If nothing else, it'll help you keep your wits about you. Hope this helps -- good luck!