Using Up Leftover Yarn: A Creative Collection of Ideas

Dear users, dear authors,
from October 30 to November 6, Leftover Yarn Week will take place, or rather the project “Turning Leftovers into the Best.” Details about current projects are available here.

I suggest that we collect ideas for using up leftover yarn here in this thread, so we can get started right away on October 30.
What ideas do you have?

I’d love to knit a shawl using only leftover sock yarn. I’ve got so many scraps lying around again. But will I be able to finish it in a week?

I’m currently doing a Tunisian crochet tissue pouch (what a word... phew) with leftover cotton yarn.
It only takes a few grams per color, so even tiny leftovers get used up.
You can also easily adjust it with more or fewer stitches/rows to make other sizes, e.g. for tampons, pads, or other small items.
Now quickly get back to it and make the most of your day off, otherwise it won’t be finished by the weekend...
Best, Caro