Fucking everything, to the point it's a problem. I replaced my windscreen wipers the other day, when I broke them to fit them in the trash can, I kept the thin metal strip that is inside and acts like a spring. I don't know if it's spring steel, but it sure is spring-y and you never know when they may come in handy.
I've got a box of boxes, all different sizes, cause you never know!, as well a bag of ziplock bags, there's got to be like 400 of them.
I've switched from Arch to Fedora about a decade ago, never had this issue with either. Actually I probably never had this issue with GRUB at all, maybe with LILO...
Where there's war, there's rape, you can ask for proof, but history teaches us that's just how it goes.