We like to travel carry-on and take the minimum needed for our stay, but we like to take (in my opinion) the best.
Here are a few of my travel essentials, all bought from Muji (mostly on sale!):
this sleep mask is super-soft cotton and nice and light - it doesn't make my eyes too dry and hot. I use it every night and bring my spare one in my purse so that I can use it on the plane and in hotel rooms if it is the least bit bright. 
this 'tiny' suitcase (a newer model to ours) is the perfect carry-on size for small airlines and Asia. We use it all the time for regular travel, since we don't like to check our luggage and prefer to only take the essentials so that we can bring goodies home with us!
I have this passport wallet in red (which was on a major sale when I went to a London location last year) and use it for my passport, e-tickets, itinerary, extra cards that I don't need in my wallet for the trip, etc. There is a nice zippered area the height of the passport wallet and a pen holder, which is so handy!
I have this recycled yarn scarf in blue. I don't like wearing scarves that are heavy or made of acrylic (and obviously not wool!), so this light cotton scarf is perfect to put in a bag or purse when travelling. It makes a fine addition to a day outfit to take it into a cooler evening.
We bought this suit/garment bag from one of the stores in Bangkok (?) and have used it a few times so far. It holds quite a few suits/dresses/jackets/pants on provided hangers (you can add more hangers of your own) and has a zippered pocket on the outside (not shown in picture) for socks and undies if you want to use just this bag for all clothes.The New York locations have an online (US) site if you want to check it out.
