Here's mine:

    javascript:for (let e of document.querySelectorAll('*')) if (/fixed|sticky/.test(getComputedStyle(e).position)) e.style.position = 'static';

I use it so many times a day it's not even funny (it's in my bookmarks bar, keyed to ctrl-2). I think it removes (or obscures) an element that I wanted to see in hindsight, way less than 1% of the time. It would be nice if I could just tell the browser to just ignore the `fixed` or `sticky` position properties entirely.