Yikes! That's a long time. They probably give you food, but i think you should bring your own because depending on what airline you have, I heard the food isn't that good.
So:
1.Eat
2.Read a magazine (with quizzes and games in it)
3.Sleep
4.Get one of those books where you fill in mad libs, do crosswords, mazes, etc
5.Play games on your cellphone (your phone can be on if its on airplane mode, which you can do in the settings)
6.Read the sky mall
7.look out the window (trust me it can be entertaining)
8. Imagine what your trip will be like
9.Go to the bathroom
10. Read a book
11. see how long you can stay still without moving
12. talk to the person next to you, or the person you are flying with
13. Normally on long flights they play movies so you can watch that
14. Listen to your Ipod and play games on it
15.fix your hair in weird styles lol
16. See how long you can keep your eyes open without blinking
17. try to add really big numbers in your head.
18. Doodle or draw
19. Make a list of things you want to do on your trip
20. Write a story about crazy things
21. Look at the cloud's weird figures and make up stories about them
22. Draw your dream room/house
23. What I do is if I have 30 minutes left in the ride, I convince my self i still have another hour to go, so that the time seems shorter.