Good reading and some really good ideas in here...I'll add a few...
I saw "pliers" for removing stuck on lids for paint jars, I use an old fashioned nutcracker.
If you fish..."Plano Stowaways" make great organizers for everything from part's to paint and tools, most of them are clear but you can also buy them in various colors.
Sharpening Steel (most knife sets come with them), one quick swipe and your X-acto/Excel blade is good to go for a few more hours of cutting.
Broken Electronics? Where to begin? I've used chips and resistors to simulate a variety of things from "LCD" screens to fuel filters...same with the wiring inside; which can be used to dress up any engine bay. After all it's already broke...
I'm sure I'll remember some more or come up with some later.
Rob