I got a neck pillow for two reasons: to use on the eight-hour flight from Charlotte, North Carolina and to use on the long and overnight train rides through the Continent. Now that my flight has ended, I am able to verify the effectiveness of a neck pillow! I have no idea why, but airplane seats are designed like scoops, but if your back is flush with the back of the chair, your head will end up sticking out from your body and the chair in an award position. If you have your hair in a pony tail like I do, your frustration will be amplified, especially with the darkness (overnight flight) and long period of time that will harken you to sleepiness.
So, although taking up the most space in my bag, the pillow is extremely light-weight, and will undoubtedly come in handy on train rides, and hopefully in hostels as a second pillow. Will include further pillow updates in my hostel reviews!
Price: <$10 USD