I sleep with a fan on for noise at home. I use a white noise machine when I'm on vacation. I absolutely can not sleep without it. The one time I forgot it, I don't think I slept all week.

Now I keep one packed all the time in my carry on. It never comes out.
I love packing folders and packing cubes. I can pack so much more and they keep my bags so organized. I used to roll my clothes in zip locks, but like the packing folders and cubes so much better.
I always put a couple of dryer sheets in my luggage to keep them (and my clothes) smelling fresh. Once I get home I throw the old ones away and replace them, then when I'm packing for my next trip, I replace them with fresh ones again.
As far as things I must carry with me:
1. roll some duct tape onto a pen--duct tape comes in handy for alot of things (fixing a hem, putting on hot spots that might blister, keeping a curtain closed, etc). With a little wrapped around a pen, you always have a pen with a nice padded barrel and neither takes up any room in your bag.
2. Body Glide to prevent chafing or blisters
3. sunscreen with a high spf
4. a good lip balm with spf
5. I have a soft shelving closet organizer I bought at Wal Mart several years ago. It hangs with velcro over the curtain rod and takes up less than a foot of space on the rod, but I can put 9 days worth of outfits in the shelves. It folds flat so takes up almost no room in the bottom or the side of my checked duffel. I always pack my clothes into a packing folder in the opposite order I plan to wear them, so they are already in outfits and in order when I place them in the shelving organizer. I hang up any dresses, but shorts/capris and blouses go on the shelves.
6. The Florida heat and humidity does a number on my already dry hair, so I bring my own shampoo and conditioner in travel size bottles. I don't like the shampoo/conditioner the resorts provide.
7. Peppermint lotion and Motrin for feet