I have extremely dry skin--bad enough to cause my flesh to spontaneously crack and bleed (which is quite painful when it happens to fingers or lips). Whenever I travel, I bring ChapStick®, various hand lotions, hypoallergenic liquid soaps and bath gel, nonirritating shampoos, etc. During a long flight, I may need to reapply ChapStick® and/or lotion several times (especially after handwashing). I won't even get into why it's a good idea to brush my teeth frequently, and have a pre-brushing rinse and/or mouthwash in my carry-on. I'll typically also have bandages (I can't use the most popular brand; I'm allergic to the adhesive) and possibly a well-known triple-antibiotic ointment (which probably falls in the "gel" category).
Also, it's not unusual for me to make several connections during a transcontinental trip. I may have as much as three and a half hours between connecting flights, with no access to anything that is not on my person, or in hand-carried baggage. Checking baggage is almost certainly a bad idea. The last time I went to Boston, my Samsonite ended up in Washington D.C., and didn't find its way back to me for over 24 hours. Fortunately, I had two days clothes in my carry-on, along with everything else I needed immediately.
There's also been talk of banning personal electronics. Except for very short trips (e.g. S.F.-L.A. and back), the one thing I've found that makes aircraft cabins tolerable is noise-canceling headphones. They aren't confiscating those in the U.S. ... yet. And yes, I do need to carry that cell phone.