My daughter loves the individual face masks they sell at Target so I’ve started putting a few of those in her stocking every year. I’ll also do candy, small denomination gift cards, and fun socks.
Costco has some pretty nice HEAD touchscreen gloves on sale right now for $9.99. They are lightweight. At my store they were mixed in with the fleece-lined ones which are not on sale. I picked up the wrong ones at first.
https://www.costco.com/HEAD-Women’s-Multisport-Touchscreen-Glove%2c-Black.product.100428176.html
On sale - even better! 
@BunsenBurner I don’t pay full price for anything! That’s why I like to start my shopping early and pick up things as they’re discounted. I usually wait until January to buy gloves that are heavily discounted, but I liked the ones at Costco - they fit my hands. Some gloves are way too long for my fingers!
@momofsenior1 Trader Joe’s has a new sheet facemask that is wonderful and is priced at $1.99
https://www.traderjoes.com/fearless-flyer/article/4345
They have many other reasonably priced beauty/skincare products that also make great stocking stuffers. I remember putting their mango shaving cream in my husband’s stocking last year.
I’ve always bombed with the stocking stuffers so am appreciating seeing everyone’s comments. 2 past years’ bombs:
the balls for the sneakers “what, are you saying my feet smell bad?” hmm, maybe not so great for a sensitive 14 y.o.,
small tools “I’m 12, what am I going to do with my own hammer?”
I’ll be filling a stocking for the first time for my Korean DIL. Any idea about what small treats she might be missing from home?
@preironic Pepero snack sticks.
I took a chance and looked up Korean stocking stuffers: The best Korean beauty stocking stuffers that are less than $15
beautytap.com/tag/stocking-stuffers/
my Korean niece came back from a visit this summer with Korean socks for everyone:
Mercari: Your Marketplace | Mercarisource=google&utmmedium=cpc&utmcampaign=1581427572&utmcontent=t0&adgroup=59126287589&network=g&device=c&merchantid=117148981&productid=m18324771226&productid=530505971161&gclid=Cj0KCQjwr4beBRDNARIsAGZaZ5dPFfAkoBL6R8ALBG13LAxOI1vXXOMORvwms1328x8dZhGd3QlgvwaAh8bEALw_wcB&gclsrc=aw.ds Amazon also sells them as does ebay
I did look up Korean snacks on line, but I thought there might be someone with first hand experience. Sometimes what the internet says and reality don’t match :).
Well, we are part of the internet. 
When I saw “individual facemasks” I thought of individual surgical masks, and wondered why those might be a good stocking gift ?
My recommendation of Pepero sticks is “first hand” knowing several young Korean nationals studying in the US.
I could see buying some snack foods from home but not really other non-edible Korean items, to be honest. If one of my kids was abroad and spending the holidays with a family, I think it would be odd to give them a stocking full of American items instead of local items. :-??
@preironic It sounds like this is your first Christmas with your new DIL. A tradition I started when my kids were little was to place an ornament in their stocking that had something to do with that year specifically. It could have been a place we visited or related to some sort of activity or accomplishment. For example, they got a little instrument ornament the year they started in the band or orchestra. One summer they learned to fly fish, so I found cute fishing ornaments, etc. If the year wasn’t on the ornament, I wrote it on with a sharpie. Now they each have their own box of ornaments, and it’s so fun to watch them decorate the tree and take a walk down memory lane.
Maybe you could start something similar with your new DIL? Possibly a Hallmark ornament every year that would be a keepsake and a way for her to remember how she was welcomed into the family https://www.hallmark.com/ornaments/keepsake-ornaments/our-christmas-together-sleigh-2018-ornament-1599QGO1736.html (example)
chercheur - good idea. They had a baby this year so lots of possiblitlies. We’ve had a couple of Christmases together but nothing in the way of traditions has jelled yet. It’s time.
Congratulations @preironic ! It sounds like you’ll have a very special holiday this year!
Mine always get socks and underwear. It’s a Santa tradition! Actually cutting down on big gifts this year and giving cash but will not cut down on stocking stuffers. Most fun to buy. To socks and underwear and candy (of course) I like gift cards, makeup to try, lip gloss, fancy tea, sometimes earrings… as someone said it depends on what they are in to. So may be hiking socks or running socks for example. D gave her BF a phone charger that’s solar power. You can hook it on backpack while hiking. Worked well when they hiked for 6 days this summer.
Luggage scales:
And I’m buying some for us too!
Everyone seems to like Bombas socks on my stocking list. D1 also likes Smartwools.