my 18 yr old slightly eccentric daughter likes card games and other games. exploding kittens, code names, or trivia games over harry potter or the office. Also, she likes umbrellas and has given them as gifts (with the gift receipt attached). fun projects: Sharpies and rubbing alcohol for cool art projects, and tye-dye kits look fun; a set of colored pencils or gel pens might be neat. Star Wars t-shirts? or other silly t-shirts. And fuzzy socks are always good.
Sharpies!
I second the suggestion of good gel pens.
Can’t go wrong with gel pens! I used to follow the hyperbole girl, but got tired of the constant deluge of profanity. I’d be careful with that one for a HS girl.
A Fisher Space pen. They come in a wide range of prices but can be had for less than 12 bucks on Amazon.
Writes at any angle. Lifetime guarantee.
We are giving our DD an adult coloring book and colored pencils. There are lots of different types of adult coloroj g books!
Thanks for all of the great suggestions! Apparently my tastes are similar to that of a high school girl because I want some of these gifts for myself. My son is trying to do more sleuthing about what she considers a bad gift. I’ll report back once he has made his choice. In the meanwhile, more suggestions are appreciated!
He sounds very thoughtful and considerate. I think he’s going to make somebody a great partner someday. Is she on FB? I don’t use it much, but one thing I do use it for is to get clues about my nieces and nephews current interests. He may be able to find out something there.
Does she wear jewelry, hats, or scarves? We have a bunch of local artisans that sell reasonably priced pieces at craft fairs. If he paid attention to her style he could probably get her a handmade, one of a kind gift that she’d be happy to use.
Are there places the kids like to go that offer gift certificates? We have a local movie theater, skating rink, and coffee house that the kids all seem to like. That might be an option too.
Just saw this. Might be good for someone interested in writing. $9 plus at the top, you can get 20% off.
http://www.poppin.com/red-medium-soft-cover-notebook-with-gold-initial-846680009373.html#
Taking the gel-pen idea one step further, my D adores fountain pens. I got her this last Christmas:
https://www.gouletpens.com/pilot-metropolitan-fountain-pen-retro-pop-turquoise-medium/p/PN91446
There are nice lower-priced fountain pens as well.
Update: My son narrowed down the list to Codenames, tea (she really likes tea), a mug, a journal, gel pens, and socks, and then was able to ask his secret santa’s father (secretly) which gifts would be most appreciated. Her dad thought that all of the suggestions would be a hit, so good work, CC! (In fact, her family plays Codenames all the time).
My son went with a tea sampler and a pack of gel pens (which cost $15 total, but he thinks it’s fair because he’s making up for last year). You also helped me with my Christmas shopping, as I bought Codenames for my family and gel pens for my friend. And I think I’ll buy some of those laptop stickers for myself… Thanks again!!!
Your S sounds like a very sweet and considerate guy. You’ve done well in raising such a thoughtful person. 
So, does he have a bit of a crush on her or is this just a friend/classmate? Inquiring minds want to know. 
Thanks for the kind words, @HImom. His secret santa is much younger (insanely intelligent) and pretty socially awkward–not a potential date or even a good friend, but someone he respects and likes. As he has matured, he has come to appreciate all of her great qualities and just wants to make sure she feels included and appreciated. I’m glad that he has internalized all of my speeches about the importance of being kind to everyone, particularly those who are different:)
You’ve done a great job, @WildLupine. We need more people like your son.
It gives me a warm glow when I see the next generation putting into practice the lessons we’ve tried to instill. :x It really makes us feel we’re getting the gang of this parenting biz.
I realize the OP has narrowed things down, but for others - this would be a great gift or stocking present: https://www.amazon.com/Sushi-Go-Pick-Pass-Card/dp/B00J57VU44/ref=sr_1_1?ie=UTF8&qid=1481412169&sr=8-1&keywords=sushi+go+go
Sushi Go is a quick card game, easy to learn and the cards are so CUTE.
I’ve played Codenames - it’s a fun game.
I don’t know if your S has bought something yet, or has time for delivery, but my geeky kids like thinkgeek.com and they have a section for gifts under $10: http://www.thinkgeek.com/interests/giftsunder10/?icpg=Holiday2015_gc_intro_giftsunder10
These are what my kids are giving their friends:
I think they are hilarious. Handi Horse and Handi Pug, and Handi Taur are pretty funny, too.
Final update: My son said that his secret santa sought him out after they did the gift exchange to tell him that the gifts were “perfect.” Thanks again and happy holidays!