Two that I keep wishing for:

(1) An easy way to download YouTube videos (preferably, any site's videos, but YouTube is the obvious target). There used to be several extensions that did this, but they all seem to have been broken by some recent change Google made.

(2) An URL rewriter: something that lets me set up a list of regex-based transformations to apply to any link I click on, redirecting me to the transformed URL instead of the original one. There are all sorts of uses for this, but the one that keeps annoying me on a regular basis is sites like DeviantArt that make you go through an "are you sure you want to leave our wonderful site?" page on every outgoing link. (I seem to recall something like this existing for Firefox, but it's been a couple of years since I used Firefox regularly and I can't find anything like this in a quick search of their addons page.)

Second one already exists.

https://chrome.google.com/webstore/detail/lacckjdlmkdhcacjdo...

Thanks! I'd searched for something like this on the Chrome site but missed this one.

I wish I had something analogous to Multifox, preferably operating on a per-tab basis.

I looked into making something of the sort, but unfortunately the necessary API calls (e.g. notify my extension BEFORE a cookie gets set) don't seem to exist, so any solution using the existing API would be a bit hackish.

EDIT: It may be possible to do at the level of intercepting all HTTP requests in the affected tabs? (No idea if the API allows that, or if it would be a good approach even if it were possible.)

Capturing still frames from a youtube video.

I see this being a hard one. I don't even know if that is possible, but I was asked by a designer a couple months ago and he even offered me some money to build that. Taking screenshots from a video source usually render very blurry images, so he was looking for an extension that would do good still images from a video at specified intervals or specific points in time. May be worth trying.

A few months ago, I wrote a proof of concept that does this: https://github.com/deactivated/video-snapshot. It seems to still work in Chrome 24.

It depends on the HTML5 player and has a few other limitations, but it might be useful for anyone doing something similar.

Boolean operators for on-page text finding. E.g., being able to search for "goose|geese", since the pluralization doesn't involve a common root.

Not so much an extension, but I would love to be able to have Incognito tabs instead of Incognito windows.

When I'm doing web dev having two sessions in the same browser is great (ie. not needing another browser open), but I often only have one tab in the Incognito window. It would be very useful if I could just have an Incognito tab in my regular window.

A better tab management. When I open a lot of tabs, the tab size is so narrow, so it's hard to find the tab that I wish.

Try this https://chrome.google.com/webstore/detail/jnjfeinjfmenlddahd...

It's helpful. Thank you.

Vertical/Tree Tabs like Firefox has Tree Style Tab.

Quick Tab is an...interesting take on the problem, but leaves so much to be desired. I'd pay money for a good Tree Tab system in Chrome. It is literally the only reason I still use Firefox for my daily browsing.

A CSS only craigslist beautifier better than this[1], I made yesterday.

[1]=https://chrome.google.com/webstore/detail/mafopckhneadngcoag...

Something that hides all the track comments on Soundcloud so the user doesn't have to do it manually on each track.

Something that would actually allow Quicktime vids to fullscreen so I don't have to use Safari to fix this problem

DownloadAll plugin from FireFox.

a syntax highlighter for plaintext gmail emails.

you mean for times when someone sends you code as plaintext email?