If you use multiple search engines in Firefox, you can not only quickly access the search bar via the keyboard but also cycle through your search engine options as well.
Just press alt/option + the up or down arrow to move through the list. When you've chosen a search engine, press enter to select it. Then type in your query, press enter again, and you're good to go. Watch the video above for a quick demonstration.
Shortcut of the Day highlights a great shortcut on various platforms from the desktop to mobile devices to the web. You can find more shortcuts here.