Shelter
The primary purpose of your shelter is to keep you and your gear dry during a windy overnight rain storm. Some hikers also use their shelter to take refuge from the clouds of mosquitoes that frequent the trail during the height of 'bug season'. Many hikers only use their shelters when the weather forces them to - opting to sleep under the stars the rest of the time. How you plan to use your shelter will be the key factor in deciding what kind of shelter to take with you on your hike.
Tents vs Tarps
The two most common types of shelters are tarps and tents. They each have their strengths and weaknesses. Which one is better for you depends upon your hiking and camping style. Tents are fully enclosed and give you lots of bug-free space. They can be set up without having to think too much about which way the wind is blowing and they provide a better sense of privacy than most tarps would. Tents - being fully enclosed - can also provide a sense of home or safety when you zip up the door at night. Though tents are heavier than tarps, many hikers consider the heavier weight to be worth the benefits and comforts of tent camping. This is especially true of hikers who sleep in their shelter most nights.Tarps are very simple and incredibly light weight. Inexpensive tarps may cost a third as much as inexpensive tents. They are not fully enclosed, so they have excellent ventilation. The same tarp can be set up in a dozen different ways to meet whatever challenges thru-hikers will encounter. Tarp camping requires more thought on behalf of the hiker. Tarps walls should be pitched facing the wind, with the edges closer to the ground in higher winds, for example.
Since tarps are not fully enclosed, tarp campers need to be more innovative when the clouds of mosquitoes show up. Many tarp campers will set up a 'tent' of bug netting beneath their tarp. Other tarp-campers might just sleep with a hat and a some bug netting draped over their face - the rest of their body being protected by their sleeping bag. Hikers who use their shelter only when the weather forces them to may prefer a tarp over a tent since - for them - the extra weight of a tent in their pack isn't worth the occasional comfort they'd get from it.
The Lightest Option
The lightest weight tarp shelter that we know of is the single person Monk Tarp by Mountain Laurel Designs. The lightest version weighs 3.9 oz. Click here to check it out.
The Cheapest Option
The cheapest tarp is one that you make yourself. A tarp made of Tyvek can cost as little as $20. You could also go to Home Depot and buy a sheet of clear plastic - cut to size - for less than $20. You can use sheet-bend knots to anchor the plastic to your tie-offs. At least one well-known wilderness instructor - and all of his students - made shelters this way for several seasons.
Less Common Options
Some hikers use poncho tarps. Poncho tarps are rain shells that double as emergency shelters. They work well for some hiking styles, but they don't work well for many hikers. Hiking in high wind and rain while wearing a poncho can be a miserable experience for some. Others express concerns about wearing their shelters; that if thier poncho rips on a branch while hiking the trail that they'd have no more shelter. For these reasons the poncho tarp isn't a popular option among PCT hikers. But some hikers make it work for them.
Hammocks are another option. Though more common on the AT than the PCT, hammocks keep the hiker off the ground at night. This is very useful in areas with a lot of bugs or very wet ground.
Waterproof bivy sacks are also a less common shelter option. Most waterproof bivy sacks have weights approaching that of more spacious shelters, and so are often passed up for the latter.