Ugh, growing up boys are so hard to shop for!
I always give my ds's toiletries, stuff they wouldn't normally get, like stinky cologne and body spray. My 13 y/o ds is into hats, so I always put a funky fresh hat in there. None of them shave, they like to be hairy, so no razors/shaving accessories. In the past, some things I put in their stockings were a Swiss Army knife, a little flashlight for his key chain, cool hemp and beaded necklaces, my older ds I gave nice, manly hemp hair ties for his dreads and dreaddie jewelry, I've given bandanas, oooh, light switch covers with their favorite sports teams for their bedroom, glow in the dark stickers of planets and stars for their bedroom ceiling, new earrings (the two older boys have pierced ears) hmmmmmm, playing cards, dice, and every year they get Uno, they LOVE playing Uno. Last year I found the CUTEST "tin soldier" nutcrackers (like from the ballet) and put those in with a small bag of nuts. They like the chocolate oranges that you throw against the wall or bang on the floor to open. I've given them the pocket watches you wear on a chain (those were a big hit!) "Manly" nail grooming kits, sunglasses, wallets, belts, McDonald's gift certificates (I know, gross, but they like to go with their friends occassionally). What else....those wrist sweat bands, 13 y/o ds plays sports so he likes to have those, and the Rasta one liked to get red, green and gold ones. A holiday themed pair of boxers tied with a bow. Hematite rings.
If I think of anything else, I'll come back.