Most long haul flight have seats with decent head rests but for shorter flights I want to sleep on, I use a soft cervical collar. More comfortable without it on but it means you don’t wake up with your head in a weird position and sore neck.
3D eye masks mean your eye lashes aren’t brushing against the eye mask.
I prefer in ear headphones as it means you can rest your head against the window or whatever, it is more comfortable and you don’t get buzzing from the plane being carried through.
I got a great travel hoodie that has heaps of pockets, some on the inside, a big hood with a fold down flap for extra darkness, ensures a comfortable temperature etc.
For shorter trips I’d recommend a moisture wicking long sleeve top to help keep you at a comfortable temperature but not take up space in your bag.
Edit: The hoodie I got years ago and still have was a Burton Sleeper Hoodie, sadly it seems they have stopped making them?