What extensions do you favor?

Adblock Plus should be a given; one of the main reasons I think people use Firefox over other IE alternatives like Safari and Opera is that Firefox can block ads, and quite easily at that. But I'm pretty sure everyone who knows Firefox knows about that.

So what extensions do you find invaluable that others might enjoy?

AnyColor is one I've recently found that I like. It's a quick theme changer, but unlike most themes, it doesn't change the shape or style of your buttons, but really, just the colors. These minor changes do not require you to restart Firefox. It comes with a dozen or so themes, or you can make your own. It can also use Mozilla Personas, which have their own extensive gallery. This extension does have two caveats: First, when you restart and it takes you to its settings page, you must add the toolbar button. If you make a few changes and leave the settings page, you won't be able to change the theme. So right-click somewhere, go to Customize, and put the button somewhere. Second, Personas support is not automatic. You have to restart a second time to enable it, for some odd reason.

GameFOX is literally worthless if you don't use the forums at GameFAQs.com, itself a literally worthless forum platform that 1995 keeps calling for the return of. I have never seen a Firefox extension do so much for such an ugly website as GameFOX. You can take all the best Greasemonkey scripts and the best CSS for a site and apply it all, and you haven't done as much by half as GameFOX does. The site lets its members only ignore 50 other users, which is ironic as they encourage multiple accounts. GameFOX's user highlighting system lets you highlight groups of users, hide their posts, or remove them from view altogether. It can bypass the mandatory "preview" phase of posting, and can add a "Quick post" to the bottom of a topic. It has a ton of CSS files to do various things and includes a CSS manager to quickly add/remove features or change the site's appearance.

Text-to-Image simply converts URLs to image files into a 200px thumbnail of the image, which increases to 400px on mouseover, and you can double click to see the full-size image. Great for message boards that do not allow images. Members of such boards commonly discover TTI, and just drop the link, and TTI does the rest. The admins are generally happy because images of whatever aren't breaking the style of their boards, dialup members are happy, because they're not installing TTI, and those who want to get the full experience of the forum are happy. Works for everyone. And if the forum you're on (*cough*GameFAQs*cough*) is so old, it doesn't support hyperlinks, Linkification has got you covered. Like TTI, it makes something of URLs. To make them play nice together, have Linkification ignore image URLs. And TTI can be problematic on sites with a lot of image URLs or certain images, I think it might be the ALT tag, that makes it render them as well. It's got a blacklist, but what it needs is a whitelist so it can only be turned on for the sites it's needed for.

Fierr is generally worthless, but it makes the error pages a bit more friendly, with a Firefox logo. I mean, you get an error, it's kind of a bummer, something went wrong, and the black text on the white seems so official, so proper. It's nice to have something a little more casual there.

Please, post more. I remember when one could spend 15-20 minutes looking at all the add-ons/extensions. Now there are tens of thousands of them. I like looking at the featured ones every now and then, but it's just gotten so flooded. Topics like this become necessary to keep Firefox fresh, get people on a particular forum who may be interested in the same kind of features to share their favorites.