Chocolates? if they are over 16 a lottery ticket, definitely toiletries, new socks etc.
DH & I still get stockings when we spend Christmas with my parents Last year they included a pristine new TEA TOWEL in DH's (to help with the after lunch washing up)!
We have always had (since we were children) tooth brushes, pens and pencils, deodorants (like impulse or lynx), a couple of little fun things like lego cars or stickers (even up to quite recently)!
But in our house, only the stockings are brought by father Christmas. It wasn't until I came on MN that I found out that in some homes, FC brings ALL the presents. I was a bit !
My sister and I decided a few years ago to do stockings for our parents in return (they were really surprised and chuffed to receive them. Off the top of my head, I think we put similar things in each, but with a mum/dad kind of slant to them. A mug, a small toy, some kind of soap or aftershave, novelty pencil, bag of chocolate coins, a satsuma and some brazil nuts...