A headlight is an excellent piece of gear to bring for each person on the trip. You can wear it while eating in the dark, sitting around the campsite with friends, or when you need to go take a toilet trip at night. Headlights have become much smaller and lighter in recent years while maintaining the same light output.
For car camping, or for those who don't mind a little extra bulk, a battery-powered lantern is a nice addition for sitting around the campsite talking and relaxing.
Most wilderness campsites are located near some sort of water source; however, the water source may be low, and its cleanliness should always be treated as suspect. Bring a water filter so that you can have cool, clear water from the stream or lake that serves as the water source. A good rule of thumb is to have one water filter per two people. Boiling water is as effective as a filter is, but it takes longer and the water won't be cold.
Whether you are hiking to a remote campsite or car camping, a camp chair of some sort is a great convenience. Purchasing a camping chair may not seem like a big decision, but if you select the wrong chair you'll quickly realize your mistake. Having a big, heavy chair when you needed something small and light, or the wrong size for your body, is a quick recipe for misery. A well-made camp chair will last for years, so consider buying the right chair an investment of both time and money that's well worth making. Some are designed to work in conjunction with your sleeping pad and are much more compact and light as a result.
First Aid & Sundries
Bring a well-stocked first-aid kit that includes a variety of bandages, dressings, blister treatments and pain killers, and know how to use them. Carry safety and security gear such as a dependable fire starter, knife and compass. You should have a map of the area and a topographical map if you plan to hike rough terrain. LED flashlights are a small, lightweight illumination source.
Think ahead. A couple of basic kits can save you if a piece of gear starts to fail: a set of spare parts (ties, fabric patches, a tube of sealant), a sewing kit and a first aid kit. Many first aid kit contents can be created on the trail if necessary, so heavy cold packs and large bandage rolls are up to the individual to include or discard.
Look for small, trial size bottles of bug spray and sunscreen. These supply two or three people for a week or more if used sparingly. Pack toiletries and personal need items (prescription medication, toilet paper or feminine products) sparingly. Finally, add a couple of reusable garbage bags to carry out trash, separate wet items or act as emergency rain gear.