An extra life straw. Or a couple of these

http://www.amazon.com/Morakniv-Companion-Outdoor-Military-4-1-Inch/dp/B004TNWD40

http://www.walmart.com/ip/Sawyer-Mini-Water-Filtration-System/29273210

http://www.amazon.com/Etekcity-Ultralight-Portable-Backpacking-Ignition/dp/B00B4FY8YO/

http://www.amazon.com/Stanley-Adventure-Camp-Stainless-Steel/dp/B005188T90/

http://www.walmart.com/ip/Unica-Stainless-Steel-Cup-18-oz./21633441

http://www.amazon.com/UCO-Stormproof-Waterproof-Replacement-Strikers/dp/B00Y4TYJTQ/

http://www.amazon.com/dp/B00FBNW0A4/

http://www.amazon.com/Emergency-Food-Rations-Calorie-Nutrients/dp/B00NGYGCH2/

http://www.walmart.com/ip/Oregon-Freeze-Dry-Beef-Stew-2-Servings/21064302

http://www.walmart.com/ip/Ozark-Trail-8-x-10-All-Purpose-Camo-Tarp/34352749

http://www.amazon.com/gp/product//B007Z1QPBA/

http://www.amazon.com/UST-Marine-Whistle-2-Pack-Yellow/dp/B00HB0U8OU/

Throw a couple bics in, some garbage bags, some paper towels, and a pack of wetwipes. You can add a firesteel, magnesium bar, and firestarters if you want. Fishing line, toothbrush, toothpaste, soap. Headnet, bugspray, hand/footwarmers depending on the season.

Med kit. Sleeping bag. I don't like the plastic signal mirrors so I pack a make up compact mirror that is pretty rugged. Throw a fork and spoon in. An emergency hand crank radio. A compass, maps. Hand sanitizer. A towel. A folding saw. A water bladder. These are all options to carry.

Wool socks, insulated hat for winter, brimmed fishing hat for summer, leather gloves to handle hot food or work in. Base layer to wick sweat away. Hiking boots. Flashlight.

I tried to list just the basics but it kinda got away from me there.