I have two teen boys 17 and 19 and two older guys 22 and 27 that I will be putting stockings together for, the contents will be more or less the same for all of them. So far I have:
Lego F1 Mini car - one of those where you don't know which one is in the box.
Lego keyring - younger two.
The two younger boys have a multi tool pen which has a ruler, spirit level, screw driver and stylus. Older two have the credit card style multi tool.
Lynx spray and shower gel for the younger two, Rock Face for the older two.
Nike socks - for the boys, Danish Endurance hiking socks for the men.
Chocolate orange and Chocolate coins obvs.
I'll keep an eye out for a few more unusual bits and bobs, the stockings are traditional size not the huge ones so it doesn't take much to fill them, plus I wrap everything that isn't edible.