Search Multiple Search engines at once Rated 5 out of 5 stars
It'll be great if we can also search multiple search engines at once. Possibly using a checkbox system as in this outdated extension. https://addons.mozilla.org/en-US/firefox/addon/9599
You simply type the query press spacebar to select the search engines(or the checkboxes using the mouse) then press enter to have them opened in multiple tabs.
In addition we can also have predefined groups to group together related search engines together. Eg. for programming related queries we can group stack overflow and cplusplus.com together.