We use a high quality electric toothbrush so to us, toothbrushes fall into the "useless junk" category. Lol I go for quality over quantity and usually end up with maybe 4-5 things to put in my husband's stocking. I never put necessities in there like razors blades, etc...I think that is weird because it is already part of the grocery budget.
This year I'm doing $5 in scratch tickets, a $25 Starbucks gift card (which I got for free through doing surveys), a new beer pint glass, dark chocolate covered espresso beans (yuck! But he loves them!), and his favorite gourmet red licorice. I may also throw in a new paperback book for him. He doesn't like magazines, but a magazine subscription is a great idea for most men and you can find a lot of good subscriptions for under $10.
I never buy items just because they fit in the stocking. That is how a lot of people end up with junk I think. This year everything happens to fit in his stocking but most years I have something sitting right below it or hanging on the side of it.
Some great stocking stuffers are new gloves, wool cap, Smartwool socks, ice scraper, favorite gourmet candy/chocolate/nuts (not just your everyday varieties but fancier brands). Beautiful hair pins are great for women as well as MAC eyeshadow, lipstick/lipgloss, quality nail polish (Zoya etc), shower gel, etc.
I have put nice collar stays in my husband's stocking before and also cuff links. If your husband grills maybe put a fancy gourmet grilling spice blend in there.