I created this user style to make my StackOverflow use much more pleasant. As the screenshots there illustrate, my sidebar contains only the "Ignored Tags" header and input box. I don't care about all of the unanswered tags, nor about all of the tags I've already ignored. Here is the CSS:
#sidebar > * { display: none }
#sidebar > :nth-child(5) { display: inherit }
#sidebar > :nth-child(5) > * { display: none }
#sidebar > :nth-child(5) > :nth-child(4) { display: inherit }
#sidebar > :nth-child(5) > :nth-child(6) { display: inherit }
This ultimately means "Hide everything except children 4 and 6 of child 5 of the sidebar." It works beautifully, but looks ridiculous. Do you care to golf, and improve my selector-fu?