Jive Search - A search engine that doesn't track you.
Context Search - Context Search is a Firefox extension that expands the context menu's 'Search for' item...
Yase - Yase is a privacy friendly search engine
Swift Selection Search - Swiftly access your search engines in a popup panel when you select text in a webpage.
DuckDuckGo - The Internet privacy company that empowers you to seamlessly take control of your personal information online, without any tradeoffs.
ContextSearch web-ext - Search for selection with your browser's search engines via a pop-up.