There are a variety of products out on the market that may add a great amount of comfort to your backcountry adventures without adding much weight.
One of our favorite products is the MSR Packtowl Ultralight. These towels weigh anywhere between 2-5 oz and are a nice item to have. We tend to throw these in our packs on nearly every trip and are great if you have a single wall tent that may experience mild condensation. Also good if you manage to get soaked in the backcountry.
Headlamps are more of an essential than an accessory. Our favorite is the Black Diamond Spot headlamp. The Spot has a variety of lighting settings, a powerful 1 watt led spotlight great for hiking in the dark, finding camp at night or hanging a bear bag. There are also three lower powered led lights that are better suited for camp use such as cooking, reading a book, packing, more general purpose use. This light weighs just three ounces with batteries, it is waterproof and will burn for up to 160 hours on a single battery.
Another great accessory item is a good pair of gaiters. We like the Mont bell Stretch Gaiters. They are best for dry climate hiking as they are made of a soft shell fabric. We use these to keep socks and foot wear clean and free from the dirt, sand, and debris that are common with wearing lightweight hiking footwear. These are very breathable but still resist bad weather.
If something waterproof is needed we prefer the Integral Designs eVent Shortie Gaiters. These are excellent for rain, spring hiking and wetter climates. The eVent fabric is the most breathable waterproof available. These keep you dry from the outside as well as the inside.