What is the most demanding wordpress plugin or tool?

I want to know the most demanding wordpress plugin/tool.
The plugin/tool that most people want.

I'm doing this survey thread to find out what stuffs are in demand and I may consider developing it and providing it for free. Do help me out.

Check my wordpress website for some tools I made - http://www.vexez.com

 

* Google XML Sitemaps Downloaded 3,435,549 times
* All in One SEO Pack Downloaded 4,817,496 times
* NextGEN Gallery Downloaded 1,738,334 times
* Contact Form 7 Downloaded 1,726,438 times
* WordPress.com Stats Downloaded 1,506,720 times
* WP-PageNavi Downloaded 668,722 times

Source: http://wordpress.org/extend/plugins/

 

You don't seem to understand my question. I'm asking for those that are not available or not really available that I might want to develop.
Not those highly downloaded ones I'm finding.

 

Oh! My bad.
I guess that's going to be different for everyone.
Personally, I have been looking for a plug in that adds additional fields to the comment section that allows readers and subscribers to add their Facebook, Twitter and Linked In profiles and displays them with little icons for each service that display with the username.

 

That can be done with Disqus. There should be a plugin for that already.

 

I have that on a couple of sites. It lets you log in with Facebook , Yahoo, and Open ID and some other junk, but it's still not quite what I was looking for.

 

Thank so much...I really need this info....

 

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