Instead I want to know about the addons you rely on that not everyone has heard of, that aren't common knowledge, the ones that you happened upon or had recommended to you by friends, and now can't be without. The secret addons that you will always use, now, regardless of what others might say.
Me, personally? I love a couple of little addons, one called GoGoMount, which allows you to use Blizzard's keybind menu, the one in the menu that pops up if you hit escape, to bind both a random flying mount and a random ground mount. I like getting random mounts, and it doesn't take up space on my (packed) bars. Another one I love is Steal, Purge and Dispel. It makes a "bong" noise and pops up a little window whenever your target or focus has something that could be removed via Spellsteal, Purge, or Dispel Magic. While there are other ways to do this, it's great to have that little reminder sometimes, particularly on my mage where I have a habit of getting distracted by Pyroblasting everything in the face.
So what are your secret addons?