What Addons do you rely on?

I was going through my Curse client today to update my addons, and this question came to my head. What addons do people rely on?
Personally, I love Bartender, although I don't find it necessary. The only time I find myself really needing it is when I need to get my glasses prescription updated and I need to make the buttons for the UI bigger...I like Omen well enough, although I don't often go in dungeons, so aggro doesn't really matter to me much. I like SilverDragon, mainly because it lets me know to be careful since there's a rare about. I do, however, find it annoying when I'm in a party with someone who happens to be taking a flight path somewhere and then all of a  sudden, SilverDragon lets me know that they saw a rare, and I panic, thinking that it's right next to me or something. Of course, with my luck, it's usually a giant spider that they see...
To be entirely honest, the only addon that I absolutely rely on is HealBot. I love HealBot. It's amazing. But even that, of course, is only turned on when I'm healing.
What about you? Are there any addons that you absolutely cannot play without?