I had some friends called up during Desert Storm, and chap stick/lip balm with sun block were gifts from heaven for them. One of our friends really had chapped lips, and we sent him a half dozen of the little blue jars of LIP MEDEX. He still thanks us years later. The lip stuff is relatively inexpensive and light in weight and fairly indestructible during the transit phase from you to them.
A friend of mine did a couple of tours in Nam. His parents and sisters sent him a sock and underwear package each week. They went to the exchange and bought a large supply of socks and underwear. They sent him an envelope with 7 pairs of socks and a set of underwear every week. He was the only Marine in his platoon that didn't get jock itch and foot rot. Foot powder is another great welcome gift.
If you are in the Navy and on a ship, you can buy these comfort things. However, books, magazines, games, crossword puzzles and even newspapers from home or the home state were like treasures.
Wonder if anyone has some care package stories for some strange or totally useless stuff they received...