Tricky age, isn't it? What hobbies does he have? My 11yo likes running and art.
Last year stocking fillers included a Facebox set, tech gloves, playing cards in a tin. Books and a DVD.
His brothers also got rugby gloves/socks, wallet, magic guillotine, torch.
This year I'm thinking about running accessories (pouch for his phone etc) maybe some art stuff and a head torch. Possibly a grownup looking washbag as he has some trips coming up.
I got my dcs reusable popcorn holders a couple of years ago, they loved them and they get used lots.