1. Compression packing cubes. More for the organization ability than the compression, to be honest.
2. Airplane foot hammock. The strap goes over your tray table, and the "hammock" cradles your legs or feet, holding them at a better angle than resting them on the floor during long flights. I used it while I was sleeping on a flight out recently, and while I was using my laptop on the flight back and found my legs and knees weren't nearly as sore as usual.