1: Tab mix plus
TMP can change nearly every behavior and action performed by tabs. With this tab, you can specify where pages will open, duplicate a tab, prevent it from closing, merge tabs and more.

2:MR local tech install
This tool can be used if you want more control over the plug-ins. It gives the user a restart button that reboots the browser quickly and re-open all the tabs that were closed.

3: All-in-one sidebar
All-in-one sidebar gives the users a sidebar and plenty of things to do with it. You can set it live to either side of the browser and use hot key controls.

4: CustomizeGoogle
This tool lets you tweak services provided by Google. Things you can do including removing sponsored ads and adding position ranking. A new feature of CustomizeGoogle gets you to stream the Web search results.

5:Gmail Space
Gmail Space is one of my favorite extensions. It converts 6 GB free online space for email to free online space for whatever you like. You can use it like a FTP program and transfer files to your gmail.