I don't have kids, but do have teenage nieces, they are easy...makeup, lotions, costume jewelry, paperback books.
I googled the question and here is what the rest of the world says:
sports cards
some sort of treat like candy or cereal bars or something that he does not often get to eat
peanuts (believe it or not, I used to enjoy getting these)
computer games
cds
mini flash light key chain (and stealing someone else's idea add a soccer or football)
one-chore-free-day coupon (I loved getting these just type This coupon is good for one day of no chores, when you want to use it, give it to me at the beggining of the day
classic candy cane!
handfull of hugs and kisses (the candy)
orange
pocket calculator
mini board game
gift card
money
some sort of clue to one of his big presents, like when I got a cd player, their was a cd in the stocking, or a computer game for a computer, ect
book, maybe a sports book (like on a famous sport player)
His own small Bible,Comic books,yo yo,gloves ,marbles,
pick up sticks,card games, fruit and candy just to mention a few.
Definitely something like rechargeable batteries and a charger if he's into portable gaming. Also, some magazines, like for x-box 360 or a guide to a game he wants for christmas. Gift certificates are also pretty awesome, like GameStop or Microsoft points, Itunes cards...
Even novelty stuff like a fart machine would probably make him happy, although stuff like that may drive you crazy.
games for a video games system he may have, batteries, earphones, itunes
gift cards, or and electronics store
gift card like best buy or radioshack
I think I'd stay away from the fart machine...lol