In Firefox you can find the search field on a page, right click, and 'add a keyword for this search'. Then you can just type that keyword in the address bar, for instance 'wp searchtermhere' for wikipedia.
In Firefox, go to Preferences -> Search and click on "Add search bar in toolbar". Also uncheck "Show search suggestions in address bar results".
Then ctrl-l will only autocomplete URLs and ctrl-k will search. Once you're in the search box, press TAB to cycle through your search providers. You can add additional search providers easily.
Slightly better still not there. If I have 15 search providers I have to press TAB 15 times to get to the last one, that is tiresome. I can search amazon/ebay/npm/rubygems/mdn/etc without looking at the screen or keyboard with chrome. I have probably >10 search engines I use daily.
I didn't think about adding sites like rubygems and mdn, but that's a good idea.
Edit: I just tried it and it works. Example: create a bookmark in Firefox and change the URL to the one below. Set the keyword to "r" in the bookmarks editor. Then you can type `r devise` in the address bar to search rubygems.
