I always pack an inflatable neck cushion.. often two.. got them at dollar store about 5 years ago and they still work fine,, I like one in small of back ( underinflated) and one for neck.
Medicines. I always take a few otcs and a two prescriptions .. yes. I know you can get otcs in Europe.. but maybe not so easy at 2 am when you need them..
Gum or candies for ears..
book or Kobo.. this year only taking my tablet instead.
Water .. always buy a bottle.
And yes. the wet cloth does work.. I get very sore sinuses from the dry air on long flights.
money/passport/ etc of course.
Usually have some cheap earplugs left over from other flights.. and a cheap eye mask.
Always buy some cheap slippers for plane.. 2-3 bucks from a dollar store,, use them just for plane., must have rubber /plastic sole so I can walk in bathroom without other peoples pee soaking my socks.. gosh .. people are such pigs. MEN sit the heck down and stop peeing on floor, and ladies who hover .. get lower or use tp on seat to wipe up your mess , you are grossing me out.