NooBox allows you to do reverse image searches with multiple search engines.
Mojibar is a menu bar based app that lets you search for emojis.
If you come across a term you wish to search or look up in the dictionary, the Inline Search & Lookup extension can help you do that without you having to leave your current webpage in your browser.
Have you always wanted to search for specific codes in the source codes of various projects? Searchcode lets you do that in over seven million projects right from your web browser.
If you have an image and you wish to see where it appears on the web, TinEye can help you find that information by letting you perform reverse image searches on its platform from your browser.