Every survival kit should have the means to provide for basic survival needs: food, water, fire, and shelter. However, there are a few additional items that can make a survival situation much easier to endure, without adding bulk to the kit.
Lip balm: Trekking for miles in the wind and/or heat will quickly dry lips and cause chapping. Having lip balm will add a much needed degree of comfort.
Hat and sunglasses: Keeping the sun out of the eyes is not only for comfort but it can be necessary to prevent sun blindness. The hat can be a cheap "gimme cap" or something a bit more expensive like a boonie hat. A hat will also help keep warmth from escaping through the scalp on cold nights.
Clean socks and underwear: Keep them in a sealed plastic bag so they stay dry. They are not only necessary for health reasons but they will provide a great morale boost. Anyone who has had to walk a distance with wet feet knows the importance of dry socks.
Hand sanitizer: If there is no soap to use, this will help keep hands germ free when eating or providing first aid.
Baby wipes: These are great for a quick sponge bath as well as if the toilet paper supply has run out.
Sunscreen: Dealing with moderate to severe sunburn is no fun after a day at the beach, let alone if it happens during a crisis situation.
Bug repellent: In many parts of the country, the mosquitoes seem big enough to carry off pets and children. Constantly swatting at bugs expends energy as well as increases mental fatigue.
Bandana: This has many uses, from a makeshift dust mask to a tourniquet. They add almost no weight to the kit and can be wrapped around more fragile items.
Glue sticks: These are excellent for making expedient repairs to shelter materials and even clothing in a pinch. Simply heat the end of the stick over a flame to soften the glue.
Gloves: A sturdy pair of work gloves will serve well when building an emergency shelter, cutting firewood, and a myriad of other camping chores. Injuries to hands can quickly become infected if not cleaned and treated properly.
All of the items listed above would fit in all but the smallest of survival kits. Most of them are very inexpensive to buy now and will be invaluable during an emergency.